NV3500 in my 74 Duster?

The ax15 has a little higher 1st gear 3:80 but is somewhat of a granny gear, 1st gear at 25 mph with 205/70-14s tires and 3.25 gears in the back is at 3500 rpms to give you an idea of where its at but that overdrive at 75 mph its alittle under 2700 rpms which is great!