I can tell you from personal experience that a small block convertor will stall to about 2300 behind a 500 (actually 514) caddy.
Thow in the caddy, and boost that. Just do something about those god awful valve springs, or you'll blow em open. literally, they're that shitty.
Give Jerry Potter a call (
http://www.cadillacperformanceparts.com), he's done some sick shit with the caddy platform. They are a GREAT bunch of guys, and I have done countless hours of personal work in their shop (buddies project car), free of charge, and even had help from them in a few places on the car. Advice from knowledgeable, older racers is irreplaceable. His son Richard is a genious as well, but had quite a scandal for a while concerning his "habit" and not turning out work. Stay away from him at all costs. He's fucked alot of people, some of who I know very well.