I need to know if the bolt pattern for 1990 torch converter will match 1980.

can I take my 1990 GMC 350 everything off the block and put it on a 1980 and make it work in the 1990

Yes you can!... It's a GM!!... Just transfer the necessary parts and it should work just fine!!... Hell, the old 4 & 6 cylinders from the early 1960's will bolt right up to the transmission!!!!.. It's a Chevy running gear... Nothing else you can do that with!!... Can't beat'em for parts interchangeability... Gotta love a Chevy!!! Especially if you do this for a living!!!!!

Awesome thanks so much for the help will keep you posted and let you know how it goes.