Chris echoes a lot that I have read a lot of posts all over about bad 400 cores - core shift (not even sure what that entirely means) and problems with cyl wall thickness (need to sonic check). Oddly enough, it seems a lot of builders avoid 4 bolt 400s like the plague and would rather have a 2 bolt block and add splayed caps. I guess the 4 bolts crack at the webs. And cracks in the lifter valley. All sorts of wierd ****.
A destroked 400 (377) always sounded like a piss load of fun in a light car.
I'm betting you could read about 400s for 2 days at Team Chevelle.