One of the easier things to do would be to buy a crate engine. It will cost a good chunk of money, but nothing outrageous. You can get everything from 289s to 408 Windsor strokers that are race prepped.
All you'd need after that is a drivetrain that can take the power. If you go with a mild street engine, an 8" rear end with your rebuilt auto (I assume a C4) will be just fine. If you go with a bigger engine that makes higher power ratings, you'd need a 9" rear with a built C4 or C6.
Just another idea for ya to throw around....
