[5.0 Pony]

I have aan all stock 88 5.0 mustang. (Except the cold air intake). I am interested in buying a set of GT-40 heads for it. It needs a little more kick. I dont want to buy rear gears or underdrive pulleys, it is my daily driver so i wanna keep it reasonable with the gas. I just want it to be faster too . There are sets of GT-40P heads on ebay for 175 bucks, what is the difference?? Also, do 5.0 Explorer's come with the GT-40 heads? Will the GT-40 heads work with the stock intake and stock headers? Also, how will the stock camshaft and speed density respond to these heads? ANy help is greatky appreciated. THANKS!!