First, a note on ordering, which is much more complicated with Thundercats than Silverhawks.

Regardless of what you may have seen on IMDb and various other sites, Thundercats ran four seasons, not two. Since the extent of the research the guys at Warner did for the Thundercats DVD release appears to have been "look it up on IMDb", the DVD's themselves give the wrong number of seasons.

(The best proof I've found for the four-season claim -- other than my own not-inconsiderable memory -- is on purrsiathunder.org. Purrsia has collected some original scripts, which are dated.)

(Also, if all goes well, you may be reading this at some point in the future when IMDb is no longer wrong. I'm trying to fix it but it's taken some time to convince the editors.)

(Update 2014-10-09: Per the excellent Hear the Roar! by David Crichton, there were two production seasons which were split into four broadcast seasons. The second production season was made up of 60 episodes and split into 3 broadcast seasons of 20 episodes, each added to syndication a year apart. Thanks to Mr. Crichton's book, I have finally convinced IMDb to fix its stupid madeup airdates.)

But it's still not that simple, because the original broadcast order of Thundercats was itself wrong, with first-season episodes airing out of story order -- notably, the Lion-O's Anointment arc aired with a bunch of episodes in-between instead of all five episodes running in a row. So there's an alternate order for those, too. Purrsia calls it the Modern Order. It's apocryphal, but I'm using it here because it makes a damn sight more sense than the broadcast order.

So, to wit, I've given three different versions of the numbering: MO for Modern Order, BO for Broadcast Order, and DVD for DVD order (which is the same as broadcast order but numbered differently).

Thundercats-Ho! aired as a TV movie and then was split up into 5 episodes. Note that numbering it as 1x66-70 is not strictly accurate, as it falls between season 1 and 2, but I'm using that numbering for sorting purposes.

So, to it.

Update 2014-10-09: Also per Hear the Roar, it may interest you to note that Julian P. Gardner is an alias used by Jules Bass. (Probably less interesting, but still notable: Bill Ratter is an alias used by a writer named Deborah Goodwin, who to my knowledge does not have any credits beyond Thundercats and Silverhawks.)

MO BO DVD Title Writer
1x01 1x01 1x01 Exodus Leonard Starr
1x02 1x02 1x02 The Unholy Alliance Leonard Starr
1x03 1x03 1x03 Berbils Leonard Starr
1x04 1x04 1x04 The Slaves of Castle Plun-Darr Leonard Starr
1x05 1x07 1x07 Trouble With Time Ron Goulart & Julian P. Gardner
1x06 1x05 1x05 Pumm-Ra Julian P. Gardner
1x07 1x06 1x06 The Terror of Hammerhand Ron Goulart & Julian P. Gardner
1x08 1x08 1x08 The Tower of Traps Leonard Starr
1x09 1x09 1x09 The Garden of Delights Barney Cohen & Julian P. Gardner
1x10 1x10 1x10 Mandora — The Evil Chaser William Overgard
1x11 1x11 1x11 The Ghost Warrior Leonard Starr
1x12 1x12 1x12 The Doomgaze Stephen Perry
1x13 1x13 1x13 Lord of the Snows Bob Haney
1x14 1x14 1x14 The Spaceship Beneath the Sands Leonard Starr
1x15 1x15 1x15 The Time Capsule Peter Lawrence
1x16 1x16 1x16 The Fireballs of Plun-Darr William Overgard
1x17 1x17 1x17 All That Glitters Bob Haney
1x18 1x18 1x18 Spitting Image Howard Post
1x19 1x37 1x37 Lion-O's Anointment First Day — The Trial of Strength Leonard Starr
1x20 1x42 1x42 Lion-O's Anointment Second Day — The Trial of Speed Leonard Starr
1x21 1x46 1x46 Lion-O's Anointment Third Day — The Trial of Cunning Leonard Starr
1x22 1x50 1x50 Lion-O's Anointment Fourth Day — The Trial of Mind Power Leonard Starr
1x23 1x61 1x61 Lion-O's Anointment Final Day — The Trial of Evil Leonard Starr
1x24 1x19 1x19 Mongor Peter Lawrence
1x25 1x20 1x20 Return to Thundera Bob Haney
1x26 1x25 1x25 Snarf Takes Up the Challenge Peter Lawrence
1x27 1x31 1x31 Mandora and the Pirates William Overgard
1x28 1x23 1x23 The Crystal Queen Leonard Starr
1x29 1x24 1x24 Safari Joe Stephen Perry
1x30 1x32 1x32 Return of the Driller Howard Post
1x31 1x45 1x45 Turmagar the Tuska C. H. Trengove
1x32 1x26 1x26 Sixth Sense Peter Lawrence
1x33 1x21 1x21 Dr. Dometone William Overgard
1x34 1x22 1x22 The Astral Prison Peter Lawrence
1x35 1x34 1x34 Queen of 8 Legs Stephen Perry
1x36 1x33 1x33 Dimension Doom Bob Haney
1x37 1x43 1x43 The Rock Giant Peter Lawrence
1x38 1x27 1x27 The Thunder-Cutter William Overgard
1x39 1x48 1x48 Mechanical Plague Peter Lawrence
1x40 1x38 1x38 The Demolisher Bob Haney & Peter Lawrence
1x41 1x29 1x29 Feliner, Part 1 Stephen Perry
1x42 1x30 1x30 Feliner, Part 2 Stephen Perry
1x43 1x51 1x51 Excalibur Peter Lawrence
1x44 1x52 1x52 Secret of the Ice King Bob Haney
1x45 1x35 1x35 Sword in a Hole William Overgard
1x46 1x28 1x28 The Wolfrat C. H. Trengove
1x47 1x53 1x53 Good and Ugly Peter Lawrence
1x48 1x55 1x55 Divide and Conquer Lee Schneider
1x49 1x41 1x41 The Micrits Bruce Smith
1x50 1x59 1x59 The Superpower Potion C. H. Trengove
1x51 1x36 1x36 The Evil Harp of Charr-Nin Douglas Bernstein & Denis Markell
1x52 1x40 1x40 Tight Squeeze Stephen Perry
1x53 1x39 1x39 Monkian's Bargain Lee Schneider
1x54 1x57 1x57 Out of Sight C. H. Trengove
1x55 1x44 1x44 Jackalman's Rebellion Bruce Smith
1x56 1x58 1x58 The Mountain Danny Peary
1x57 1x60 1x60 Eye of the Beholder Kenneth E. Vose
1x58 1x47 1x47 The Mumm-Ra Berbil Jeri Craden
1x59 1x62 1x62 The Trouble with Thunderkittens Kimberly B. Morris
1x60 1x63 1x63 Mumm-Rana Bob Haney
1x61 1x49 1x49 Trapped Stephen Perry
1x62 1x54 1x54 The Transfer Lawrence Dukore & Lee Schneider
1x63 1x64 1x64 The Shifter Matthew Malach
1x64 1x56 1x56 Dream Master Heather M. Winters & Annabelle Gurwitch
1x65 1x65 1x65 Fond Memories Lee Schneider
1x66 1x66 2x01 Thundercats-Ho! Part 1 Leonard Starr
1x67 1x67 2x02 Thundercats-Ho! Part 2 Leonard Starr
1x68 1x68 2x03 Thundercats-Ho! Part 3 Leonard Starr
1x69 1x69 2x04 Thundercats-Ho! Part 4 Leonard Starr
1x70 1x70 2x05 Thundercats-Ho! Part 5 Leonard Starr
2x01 2x01 2x06 Mumm-Ra Lives! Part 1 Leonard Starr
2x02 2x02 2x07 Mumm-Ra Lives! Part 2 Leonard Starr
2x03 2x03 2x08 Mumm-Ra Lives! Part 3 Leonard Starr
2x04 2x04 2x09 Mumm-Ra Lives! Part 4 Leonard Starr
2x05 2x05 2x10 Mumm-Ra Lives! Part 5 Leonard Starr
2x06 2x06 2x11 Catfight Chris Trengove
2x07 2x07 2x12 Psych Out Sandy Fries
2x08 2x08 2x13 The Mask of Gorgon Romeo Muller
2x09 2x09 2x14 The Mad Bubbler Kimberly Morris
2x10 2x10 2x15 Together We Stand Herb Engelhardt
2x11 2x11 2x16 Ravage Island George Hampton & Mike Moore
2x12 2x12 2x17 Time Switch Sandy Fries
2x13 2x13 2x18 The Sound Stones J. Larry Carroll
2x14 2x14 2x19 Day of the Eclipse Kimberly Morris
2x15 2x15 2x20 Sideswipe William Overgard
2x16 2x16 2x21 Mumm-Rana's Belt James Rose
2x17 2x17 2x22 Hachiman's Honor J. Larry Carroll
2x18 2x18 2x23 Runaways Bill Ratter
2x19 2x19 2x24 Hair of the Dog Chris Trengove
2x20 2x20 2x25 Vultureman's Revenge Herb Engelhardt
3x01 3x01 2x26 Thundercubs, Part 1 Peter Lawrence
3x02 3x02 2x27 Thundercubs, Part 2 Peter Lawrence
3x03 3x03 2x28 Thundercubs, Part 3 Peter Lawrence
3x04 3x04 2x29 Thundercubs, Part 4 Peter Lawrence
3x05 3x05 2x30 Thundercubs, Part 5 Peter Lawrence
3x06 3x06 2x31 Totem of Dera J. Larry Carroll
3x07 3x07 2x32 Chain of Loyalty Bill Ratter & Peter Lawrence
3x08 3x08 2x33 Crystal Canyon Sandy Fries
3x09 3x09 2x34 The Telepathy Beam Kimberly Morris
3x10 3x10 2x35 Exile Isle William Overgard
3x11 3x11 2x36 The Key to Thundera Matthew Malach
3x12 3x12 2x37 Return of the Thundercubs J. Larry Carroll
3x13 3x13 2x38 The Formula Kimberly Morris
3x14 3x14 2x39 Locket of Lies Bill Ratter
3x15 3x15 2x40 Bracelet of Power Bill Ratter
3x16 3x16 2x41 The Wild Workout Becky Hartman
3x17 3x17 2x42 The Thunderscope George Hampton & Mike Moore
3x18 3x18 2x43 The Jade Dragon William Overgard
3x19 3x19 2x44 The Circus Train William Overgard
3x20 3x20 2x45 The Last Day J. Larry Carroll
4x01 4x01 2x46 Return to Thundera! Part 1 Peter Lawrence
4x02 4x02 2x47 Return to Thundera! Part 2 Peter Lawrence
4x03 4x03 2x48 Return to Thundera! Part 3 Peter Lawrence
4x04 4x04 2x49 Return to Thundera! Part 4 Peter Lawrence
4x05 4x05 2x50 Return to Thundera! Part 5 Peter Lawrence
4x06 4x06 2x51 Leah J. Larry Carroll & David Carren
4x07 4x07 2x52 Frogman Kimberly Morris
4x08 4x08 2x53 The Heritage Bill Ratter & Peter Lawrence
4x09 4x09 2x54 Screwloose William Overgard
4x10 4x10 2x55 Malcar George Hampton & Mike Moore
4x11 4x11 2x56 Helpless Laughter Matthew Malach
4x12 4x12 2x57 Cracker's Revenge William Overgard
4x13 4x13 2x58 The Mossland Monster Chris Trengove
4x14 4x14 2x59 Ma-Mutt's Confusion Beth Bornstein
4x15 4x15 2x60 Shadowmaster Dennis J. Woodyard
4x16 4x16 2x61 Swan Song William Overgard
4x17 4x17 2x62 Touch of Amortus Bill Ratter
4x18 4x18 2x63 The Zaxx Factor Matthew Malach
4x19 4x19 2x64 Well of Doubt Dennis J. Woodyard
4x20 4x20 2x65 The Book of Omens William Overgard

This post originally used Stuart Langridge's sorttable but was updated 2014-10-09 to use jQuery, tablesorter, and parser-ignore-articles, and then on 2015-09-25 to use Mottie's tablesorter fork; icons courtesy of Font Awesome.