Ok, now Im not planning on putting heads on my mustang but, rather would like a clarification. Ok, so while browsing through the Ford racing parts cataglog I saw a set of gt40X al heads, that I belive were 625$ per head. Now this is a pretty good price compared to some other guys out there. I looked at Holly, Edelbrock, AFR, Canfiels, Brodix etc... and for what you get out of the gt40's its not even worth looking at the other guys unless you are planning on huge power, in which case the stock 302 block would not even be able to handle. SOOOO WHY all the fuss about gt40 heads being crap... I understand mabye the cast iron heads might not be as good, but the aluminum ones seem to be giving the other guys a run for their money and its a true bolt on.

 

There are certain differences between manufacturers, each one may or may not have advantages over another. It really depends on who your preferred head manufacturer is. As you said the aluminum GT-40x is a good head which makes great power and is competitively priced, but keep in mind that this head is considerably better than the GT-40 iron heads are in as-cast form. You could of course make a run-of-the-mill GT-40 (or even an E7) head flow very well with some nice port work, but in most cases it's more cost-effective to buy a better-flowing head to begin with, also when people ask you what you've got, it sounds better to say you're running "AFR's" than "ported GT-40s".
It's all a matter of taste and what the car is built for.