Whats the difference in GT40 and GT40P Heads?
 

I need a budget set of heads and am wondering whether or not to just port my E7 heads or maybe look into the GT40P heads. Why are the GT40P heads so cheap over the other GT40 heads? I don't know too much about heads so any info will be appriciated. My car has a low/mid cam, TrickFlow Trackheat intake, 70mm throttle body, and underdrive pulleys. Also is moving to 24 pound injectors going to be worth doing with my setup, and if so will there be a big gas mileage drop(this is my daily driver) thanks guys for any imput.

A lot of guys are making good power with P heads. The main difference is the spark plug location (thats why they make special headers), and valve size. For what your going to run they should work good, esp for the price. You could probably run the 19# injectors but the 24s should work alright too with the correct MAF

The p's are not really more expensive than the regular iron 40's, the p's need a special header to clear the plugs because they have a different location, also a smaller exhaust valve on the p's, but they flow a little bit better then regular 40's due to the plug relocation, of course mine been ported anyway so they flow alright..... also the springs suc on the 40's, so upgrade them if you want some real power.
the injectors? you can stay with stock 19's for a good while, i just now upgraded mine to 24's, the 19's were pushing me in the 12's with no problem, start with a fuel pressure regulator if you dont have one.