Talk to the guys at
Bowtie Overdrives. They can help you figure out what you need.
I'm a little worried about your axle ratio choice.
If you're running 28.25" tall tires (e.g. 225/75R15), then your 60 mph cruise in OD will be about 1360 rpm. I'll bet that's too low for your motor's torque band. I think you'll be better served with a 60 mph cruise rpm in the 1800 - 2000 range.
regards,
Leon
