No one really exactly answered the question at hand. He did ask about a 400, I didn't see anythoing about him wanting to stroke it. If he's thinking about cutting heas for comprsion or new pistons, inexpensive seems to be the way of thinking here
He asked for combinations, the 451 is the best, especially for a budget build. I think the point of the answers is that if he's going to go through the effort of getting new pistons and cam which would require some level of machining/balancing, ($) might as well try to find a 440 crank and have it made to fit. A 440 crank surely can be found cheaply enough, probably for $150 or less. Bet you could find someone to literally give you a cast one. (400 cranks are cast) The rods can be re-used so it's just the extra cost of the crank and to cut the 440 mains down. You'd have a stout short block that will likely be a much better performer than just sticking new pistons in a 400.
But if that's not an option then yeah, get new pistons. Cutting heads for compression is a band-aid fix to an inherent performance flaw. You can always get the heads cut at a later point.