I don't know if you ever said whether the car is a 5-speed or auto. Foxes can run low 12s on your engine combo. (one of my good friends ran 12.30s with that combo back in the '90s) It's all about the hook though. You've got a decent amount of power. If you plant it, the car will easily be in the 12s. I ran 12.91 @ 103 with a stock 302 in my '89 LX. Here's an article I wrote about it:
http://www.mustang50magazine.com/featuredvehicles/m5lp_0812_1989_ford_mustang_lx/index.html
I'm all about the boost. Nothing wrong with nitrous, but here's what I did:
http://www.mustang50magazine.com/techarticles/m5lp_0910_1989_mustang_lx_upgraded/index.html