I think you have something backwards. iron doesn't tolerate the higher compression ratios because it holds heat. alum sheds heat and you can get by with a little more on the street but I never use the "1.5 points higher" the internet/magazines tell you. an iron head, with everything equal will make more power. "everything equal" is the issue. I've always thought the greatest advantage to alum is it's much easier to repair. I think the whole thing is more complicated than people want to get into. chamber design, piston configuration, plug location, etc. can you control the heat the engine makes or is it a problem? I have a set of iron heads I firmly believe make more power than the edelbrocks i'm using, but the edelbrocks burn cleaner and they're easier for plug changes. I don't think the whole issue is cut and dried and I definitely don't prescribe to the culture that alum is always the way to go. keep in mind that the top of the piston is the bottom of the combustion chamber and the bottom needs to match the top for best efficiency. if this is about the 383 your working on, then things do get narrowed down a bit. a 440 is more flexible with parts selection.