Dave Freiburger once said, “Afford the best head you can.” I have to agree with this. Since the cylinder head is where the power is allowed to be made or not. This goes for any engine displacement.
I get what your saying in terms of not over buying. But you are in a catch 22 when it comes to making lower. Skip the better head and use more cam to obtain more rpm’s or spend on a better head, use less cam, make more street usable power. That equals less converter and gear.