So I have a 77 302 that is going into my mustang, I've mentioned this before. I have the factory 289 that came out of the car, would I be better off putting the 289 heads on the 302 or should I leave the 302 heads on it? The 302 heads were obviously during the smog craze and they're out of an f100 from the time. I just want to know if anyone thinks it would be better to go with the 289 heads or not. I could probably get them ported and polished and make some better power with them. Would I see a power gain from switching to the 289 heads, since they're pre smog?