for good info, check out the tech section at jason.fletcher.net . and since i don't think he has head specs posted, here they are: stock "E7" heads have 58cc chambers with 1.78 intake/ 1.45 exhaust valves and 124cc intake runners. don't go back to the 10" clutch, the 95 clutch is far better. don't bother doing a new cam first thing, the stock one is pretty good. full exhaust mods should come first, fooled by a new intake like a weiand stealth and then a good set of aftermarket heads. oh, a full tune up would actually be the best place to start if you haven't done that yet.
If it's not broke, you're not trying hard enough.
1983 Mustang GT T-Top.
New T5 installed, driving my 'Stang again.