Not much. Eibach springs, Tokico shocks and struts, Maximum Motorsports caster/camber plates and a good set of sway bars. Solid rear control arms help too.
Throw on a set of subframe connectors to tie the front and back end together.
But while your are at it, might as well upgrade to the 5 lug set up and install a set of SN95 Cobra brakes. Use the '93 Cobra master cylinder, but check thread patterns carefully. Ford was notorious for using a combination of SAE and metric threads, to include brake fittings throughout these years. I think the '93 MC was still SAE. I did this on my '95 and I think it was the '94-'95 Cobra was metric, while the GT was still SAE. So I had to go with the '93 MC.
Vendors like Steeda have a lot of great chassis performance parts. If you get serious, I have a set of SN95 spindles I could make you a deal on.