Most guys are going to ask you how much money you have and what you want to do. If you have infinite resources, buy a supercharger. If you have limited resources and want to build a streetable stang, then there are some good mods. First, buy 4.10 rear end gears for your automatic. This will cost you $135 for the gears and another $200-300 for installation. You won't regret it. Second, buy a chip or programmer to modify your timing and air/fuel ratio. This will run you anywhere from $300-400. Third, buy long tube headers. Since you have an automatic, you will need to go with Kooks, Hooker, or MAC. The headers will cost $500-700, with another $600-800 for installation.