318 help..

I used the Engine Quest heads on my 318. Very happy with them so far but i had to change the valve springs because the ones that come on them would bottom out before full valve lift. I guess I should have bought the heads bare and gone from there. I'm running the Comp XE268H cam but would like to try out a Comp 280H. Has the same lift but more duration. Hot Rod Magazine built a similar setup with better pistons and made 400 hp.