The vacuum powered super awesomely weak link of a transmission that only the N/A '97 GT's got...sucks.
If you don't plan on tossing at least a decent trans in it, don't bother with modding it.
Find another car or get a built trans.
New solid lower mounts, Poly Uppers mounts, Solid sways with poly bushings, Aftermarket trailing arms, 180* T-stat, get that PCM tuned, have the u-bend deleted and toss a high flow filter in it. Past that, STB's (which really don't make much of a difference), struts/springs/wheel-tire combo will pull everything together.