What's your budget? A big-block is wide, so you will need to move steering and maybe other things, too. If it were me, I'd get all the suspension stuff done first, to make room for the motor.

There are a few hotrod shops out there that put stroker cranks in 400 blocks and get 415 to 427 cubes out of it. It's not cheap, but neither is a pro-stock 454.... 8-)

A TH350 might not be strong enough unless it's built up a lot; maybe a TH400 would be better?

If it were me, I'd run a small blower on a 350, instead of a big block. Plenty of HP, and I bet it's cheaper....

Cheers!
George