I used my stock 904 behind a 98 5.9 with a B&M flexplate. I put a carb so no notching the bellhousing for anything. Also, use the small starter. Oh yeah, I have a volare so its just about the same as an A body underthere.

76' Volare, 5.9 magnum w/Iron heads. New best 10.68 at 123 mph 1/4 mile.