there are a # of options here , if you use the OD 833 4 spd when you convert 3.91 would be my choice , as you will have tons of low end power & still have around 2.80 for the highway , if you are going to a regular 833 3.23 or 3.55 aree good all round gears , it really depends what you want the car to do & how much time you spend cruzin , city commuting or highway driving