Cliff Ruggles (SP) is the guy to send a Q-Jet to. I haven't sent him one yet, so I can not comment from first-hand experience. However, he is very well respected and gets a lot of accolades on the "Performance Years" Boards.
If you put that kind of meat behind a 10-bolt with 3.55 gears, expect to lay out some cash for some axles. You might be better off with some 3.73 or 3.90 gears, but you'll have to forget about cruising at anything over 65 MPH.
I've got a 10-bolt 3.55 behind a 455, and I prefer to have really bad 60-foot times with scorching trap speeds by running relatively skinny tires rather than upgrade to a 12-bolt or buying expensive axles. Pontiac's 10-bolt is stronger than most other rear ends of about the same size, but it still has its limitations.
Make sure you're building the motor for the type of driving you'll do 99% of the time, and not for the other 1%.
