915 heads vs 302 heads

I thought I did good getting the 915s. I figured the 302s would be less productive coming out of a mid 80s vehicle with all the emission crap on it. The car is strictly for the track and want it to be productive as possible. I eventually want to do a 318 stroker would I be better off using the 302 heads or the 915s? What direction do I go now?