[chiphead]

That 455 shortblock sounds like a good combo for a fair price.

The problem with dishing the pistons too much is that alum heads can tolerate more compression than iron for a given fuel. So if you dish for 9.5:1 with iron, you're stuck with that compression for alum heads with 72cc chambers. Flattops with aluminum heads can run 10-10.5:1 with properly chosen cam and machine work. And that makes more power everywhere.

It's been my experience that having a set of factory irons totally rebuilt and street ported will cost about $1500-2000. So compare that cost to a set of alum heads, and see what the budget shakes out.

Choose engine size, HP desired, compression ratio and pistons/heads. Piston choices change as engine size changes. Head selection changes based on compression, piston choices and HP desired...

Also consider the support systems for the engine. You WILL need to redesign the fuel system to support over 375 HP. Headers require moving the brake lines around. You will need a healthy radiator, shroud, fan, 11 bolt pump, etc. Good torque converters are $400-700.