http://www.masteruni...o=&FactionAuto=
That is a pretty accurate list of what mechs were built up to 3050 barring some of the wierd prototype and experimental stuff. You can poke through there and at least find out which mechs don't have more than two variants, but it isn't obvious which variants would be identical in MWO, so it still would take some extra cross-referencing with Sarna or some sourcebooks. It also treats special 'named' versions as a separate variant, so keep that in mind.
Some of the ones I remember being problematic at 3050, off the top of my head:
Axman
Hatchetman
Panther
Pillager
Javelin
Woodsman
Talon
Thug (Has 3 variants, but all would be identical in MWO)
Lynx
Dervish
I know there are more, and I'm not even thinking about the mechs with only a single variant.
Edited by Maxx Blue, 30 September 2014 - 09:55 AM.