Muscle Car Buildup
A GM crate motor from a dealer such as Scoggin-Dickey, Burt Greenwald or others will run you about $4600 for a 454 big block with 425 hp. At that level, I'd suggest a 12-bolt rearend from Currie, Mark Williams etc. as that will make the hookup to your chassis easier. As far as daily driveability is concerned, I'd forget a Turbo 400 and think of the more modern GM trans as you could run something like a 3.91 or 4.11 diff but take advantage of the overdrive ratio and have a lot smoother cruising on the Intestate.