I have a 91 trans am GTA and I did some upgrades in terms of chassis and suspension. First of all let me write the list that I have done to my car...
spohn subframe connectors,
spohn lower control arms
TDS wonder bar
Moog springs,
Tokicko Illumina Adjustables (5 different)
Energy Suspension Polyurethane Kit
Let me add some photos...

First we had to take off all the trim part to reach back shock absorbers heads...

 

......

 

After we replaced some parts...

 

After we installed the polyurethanes...

 

Wonder Bar, shock absorber and its adjustable head...

Hope you have some clues about upgrading the suspension and chassis,

By the way we installed the subframes when the car is on the ground not on the lift, because we wanted to keep the car as it is on the ground not in the air...