aluminum subframe bushings kick ass
you really need someone to check it out for you if you can't to see what all is wrong with it. There are quite a few bushings or other problems that could give you the symptoms you describe
you need to check your rack bushings, subframe bushings, tie rods, wheel bearings, ball joints, strut rod bushings, control arm bushings, and strut rod bushing recievers welded onto the front of the subframe. All of those or one of them could be bad. That is where to start.
The A/c is harder to say. Start with verifying it is charged, check to see if the compressor clutch engages, if it does not, check to see that it is getting voltage to turn on. Again a multitude of problems could be at fault here.
fix all your bushings, get ALSFB's, get a good alignment, get some decent tires, upgrade the brakes/knuckles to the 96-99 SHO 11.6" front brakes, fix any coolant leaks if u have some....... you'll like the SHO a lot more with a few choice(and inexpensive) mods and just upgrading worn out 20 year old components......
I'd also look into the size of your swaybars and upgrading to something different, this can make a nice handling improvement by just swapping out stock ones from a junkyard. I have 20.5mm front swaybar and 26mm rear swaybar so it turns in crisp and has SOME traction in tight turns. I think mine stock had 24mm front and 23?mm rear.... it was a nose heavy pig that sucked in handling..... the later years of SHO all vary with swaybar sizes in a random fashion. I don't think their is a method to the madness of what came with what.