I would upgrade to a later model ford alternator. Like one off of a 94-95 mustang. It will bolt right on with little trouble and puts out 130amps vs 65 amps (87-93 stang). There is some slight grinding that will need to be done to your bracket and a heavy gauge (4awg) charging cable will need to be run to handle the larger output.
http://66.70.5.241/8793mustang.pdf
You can get one from a parts store, but I wouldn't recommend a reman alt to a mustang lover. I think PA performance's new 3g alternators are the same price anyway.
http://www.pa-performance.com
If you really want to go overboard like I did... check out
http://www.mean-green.com I guess I got a little fed up after going through 3 reman alts. This sucker puts out 100amps at idle.
Good luck
Brad