By GM 366 do you mean a Chevy big block 366?

If so, I believe the heads severly limit breathing, so its not popular in hot rod circles. But if you replace the heads and manifold it should have some potential.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...