Welcome to :SNSign:
Just ignore the bad attitude some have around here.
If your 96 is an auto I recommend 4.10's, if its a 5spd I recommend 3.73's or 4.10's.
As for the PI swap, many have proven lately that just doing the PI cams/ PI intake will get you about 5-10hp away from the 99+ PI motors. And its still safe to S/C down the road if you want. And if you want even more power you can buy some comp cams or VT cams and make more power than the PI swapped cars for less money(with new parts).
Just to through out some info for ya.
BTW don't let the younger immature people scare you away, there are alot of intelligent people here also...
props to all who did not jump on the "Search n00b" bandwagon. if it wasnt for new members asking questions, we might as well just make one big mustang how to tech article and get rid of the forums alltogether.