Are you hard pressed on an automatic and a 400/455? If you are going to do all that work anyway, why not go a little more modern. I read a slick article in Hot Rod where they put an LT1 350 and a T-56 tranny w/ a 3.73 rear in a 70 Camaro z-28. The car had the classic muscle car look (well, at least for a Camaro) with a modern drive train, not to mention 20+ MPG. I've read about people getting 400+ HP out of those LT1s with out doing anything too difficult.
