Re: SMALL BLOCK 400?
A 400 will wake that car right up, 400s are torque monsters. There will be a noticeable difference from a 305.
The only thing I can tell you is that if you put non-400 heads on it drill the steam holes in whatever heads will be going on it (the 400 has siamesed bores). The 400 got a bad rap from people running them on the street with aftermarket or other than 400 heads without stream holes drilled so they overheated in stop and go traffic, so drill the steam holes unless your running a track only car. Some say the 817 casting blocks are weak (high alloy 509 castings are the best) but unless your planning 8 second 1/4s that block will be fine.
Finally got a thirdgen (06/21/09).