915 heads vs 302 heads

Well that's what im running. I have a 28 in tall tire with 4.56s right now. I thought it was too deep myself but I was happy on friday when I went through at 5800. I know the 318s can scream higher than that if needed and its at the point where im starting to run out of cam so its perfect. So the 915s are a better rpm head if I had the head shaved or a decked block? Im going to look into the rhs for valve and runner size. I was trying to do it the cheapest way with the best performance. I know cheap and performance don't go together usually.