SHELBY GT 350 Member
Joined: Sep 2010
Location: see user name
Really depends what you want out of the car and of course budget.
Rearend gears and suspension mods like lower control arms are always a good start and bang for your buck. If you want any real power out of it then PI swap, which is the heads and intake from a 1999+ Mustang. Beyond that, once you get into the bolt ons many of them aren't as effective as their advertising suggests - some are still good but at least a few are completely useless. Kind of a broad subject for me to attempt covering in a single post, but if you do a little looking around on here (search button) most of this stuff has been covered ad nauseum. Whatever you can't find, feel free to ask.
2001 GT Convertible
All the usual bolt-on's /200 I6, C4
And a few Explorers too... 2008 4.0 XLT 4x2, 1996 XLT 5.0 4x2, 2003 Sport Trac XLT 4.0 4x4