906 or 452 which is best overall

Thank you for the advice IQ52! I made a mistake on what I said though, I actually have two complete separate builds planned. The first being a mid to high 11's which would consist of a .030 bored block with the stock steel crank and rods, forged flattop pistons, cut the deck and/or mill the heads to achieve a 9.5-10/1 CR with the 452 heads mildly ported and polished, this hydraulic flat tappet camshaft, https://www.summitracing.com/parts/cca-k21-225-4 we have an edelbrock torker intake manifold and a Holley 800 DP and a 3000 stall converter.

And the second build (which probably won't happen because of our budget) being the same block, the same steel crank, eagle rods, the same pistons with the 75 CC EZ-1 Indy heads with the deck cut to achieve the 11/1 CR, this camshaft, https://www.summitracing.com/parts/lun-20230713k an M1 intake manifold and a 950 CFM Holley ultra XP carburetor.

I forgot to mention that with either build we plan on installing ARP main studs, ARP head studs and ARP rod bolts. Because if we build the iron head hydraulic flat tappet engine then it's getting a nitrous kit that's adjustable from 100 HP up to 250 HP.

Chances are we'll be building the first combination so I'm hoping to be able to cut the deck or mill the heads enough to achieve a 9.5 or 10/1 CR with a flattop piston. We were going to just buy a rebuild kit that has domed pistons that make the CR 10.34/1 with the 452 heads but I've read that it's much better to use a flattop piston if possible because of the flame travel in the combustion chamber.

Thank you so much again for your advice and information! I enjoy reading and getting other people's suggestions and advice because there's always something to learn!

I hope that you have a great day! :-)