The key question is what you want the car to do. If you are looking to cruise around, behave with speed limits and hit the occasional 100-110mph, I would go with the 3.55s. As stated above, higher numbers will virtually eliminate first gear or make you really good at 1st/2nd powershifts.
If you want to race top speed with vipers, vettes, ... you will need more power and something even lower (3.08/3.27). But if I remember right when they were new the published top speed of the Foxbody was 145 or 149. At that point you have aerodynamic drag to deal with if you want to go faster (not just gear ratio and RPM math as used above).