Wow man, cool find. As said before keep it original. My old 89 Saleen mustang California Edition was destroyed by the guy who bought it from me. It was a stock mustang GT that they sent to saleen, had a TON of suspension work done to it, braced the frame so it had ZERO body roll, new coils new control arms and a bunch of parts, adjustable shocks, short throw shifter, and then countless engine mods. I sold it bone stock just as it should have been. (had one of a kind BBS 3 piece wheels which was rare for '89) but the guy riced it out and took off the lights, took off the hood and put a stupid cowl unpainted glass hood, euro lights in the rear , and lots more. Only thing I did to it was make it a 2 tone interior and got high end black custom made leather seats front and rear and did a black carpet kit and made the door panels to the floor black. From dash up it was dark gray and looked SWEET. Makes me sad when I see it driving around now.
I had a sweet rig like yours and wish I never had gotten rid of it so take that and think about it!