Classwise you can go FS and get murdered by the new shelbys or bullets, STU and get killed by rally monsters, ESP and be a bit short on power to the newer ones, or CP and go hog crazy building a trans-am car out of it.
STU and ESP are similar, so you can use STU as a stepping stone (Rcomps are biggest difference)
Find out what the springs are, if they arent H&R or something like that, throw them away they are weak. Probably go ground control coilovers (weight jack type setup) if you have to go new.
Get caster-camber plates.
As far as shocks, save your money and go Bilstien or Koni, others just arent that good unless you spend a lot more.
Swaybars, I run a BIG front bar (35mm if memory serves), it sounds backwards, but it helps limit front camber loss.
If you have time/$$ go poly bushings in the front, but dont upgrade the upper rears, they will bind (factory replacement only good choice)
Rear suspension, you can go MM lowers (watch the rules with bushing materials) and add a MM PHB, OR get the steeda 5-link (which alters the geometry, but costs something like $1200) which I see as the best solution.
LSD, your going to rebuild every once in a while (depends on how much you run it, I have heard of several times a year to every 2 for serious autocrossers) with the stock traction loc, its just not up to autocross abuse. There is an alternative packing order for the clutches that you can use that tightens it up. I went to an Auburn, but have been having problems related to the install.
That list with some allowed motor play would make a fun STU/SP car