It’s really pretty easy.......
“Correct” castings for heads, intake, exhaust, carbs.

You can do anything to them that doesn’t appear incorrect when the motor is fully assembled.

If you’re not a front runner type car, then using the exactly correct heads, intake, carb, etc isn’t quite as important.

For example, if you have a 70 GTX 440 4bbl combo running 12.70’s, no one is going to be upset that you have 452 heads on the motor instead of 906’s.