Got a 2004 LS1 out of a vett that had a 6 sd manual sticking it in a gen 1 Firebird. Can one rework the original flex plate to work with a 200 4 auto transmutation? Or what are my options?

 

Yes You need the flexplate/flywheel spacer and longer bolts and You need a flexplate from a 1997-2003 with automatic ,,,,,,,,it's easy to spot as it has a curve to it ( the flexplate that is ) and You can only install 5 tranny to engine bolts .

 

Haha! "transmutation", I like that...

Anyway, if we ASSume this "original" flexplate is not from the manual 'vette but from the 200R4's donor vehicle, then it's not likely to fit at all. I have this exact combination, I used a flat LS flexplate, the crank spacer, and 6 new (longer) bolts. It's been long enough ago that I no longer have the part numbers, but they are available on here using the search function.