400s can EASILLY drop in a 440 crank and you suddenly get 451 cubic inches, because the 400 has a bore that's .090 larger than a 383, although other than that, the 383 and 400 are pretty much identical. the 440 bore is .070 larger than a 383, or .020 smaller than a 400.
there are kits that you can pick up for about $1800 that will allow you to make that low compression, dog of a 400 into a high compression 500 inch monster. pick out the right heads and cam, and you're looking at an easy 600-650 hp on pump gas.
total cost to build such a monster, is probably about $6K though, after block clean up machine work, plus clearancing if needed, stroker kit, heads, intake, cam, headers, carb, etc.
or you can get some aftermarket or custom pistons to get the compression up in your 400, pick out a good cam, buy a set of $800 aluminum stealth heads from 440source, and you're looking at 450-500 hp for about $3,000
