I have a 99 mustang v6 and these sites will help you out with anything and everything. suggestions as to what to add on. I would say with out getting really involved and try and stay simple just get new headers, exhualts, ram air cold air, under pull from steeda the harmonic balancer one, 3.73.1 ring and pinion gears if you get 4.10 your highway driving is going to suck. If you have any other question shoot me an email
michael@hostglobe.com ill be more than happy to help.
http://www.3.8mustang.com/ http://rpm-mustangs.com/ http://www.supersixmotorsports.com/