What would you build if limited to 372ci - with boost as an option

I would only choose the big block for the physical strength of the block itself. The very first thing you need to do is work out some math and decide how much power you need to get where you want. Then decide what path gets you there. A small block making 2.9hp/ci is a hell of a thing (~1100hp@372ci) and it’s possible but for longevity an aftermarket block may be the best decision at that point if staying small block. A big block might be better for a stock block choice in that case. And a gen 3 hemi might be the best of both worlds. Don’t forget you can pull plug wires and make runs at a lower displacement so building 372 for a 372 class may be the wrong choice. A 454 with one wire pulled is 397. So you could possibly fit the car in multiple classes if you think that way. Engine builders hate that though. First thing first, how much power do you need?