Depends which rear you have, and what shape the rear is in.
Do you have the Ho33 rear which has a round cover and a dropout style pumpkin. 3.90:1 gears are most common with this rear
Or
Do you have the spicer 45 rear that has an elongated octagonal looking cover. 3.07:1 gears are the most common gears in this rear?
I am assuming your jimmy is a 1/2 ton, and not a 3/4 ton with the eaton ho52 rear. Most common gears in the ho52 would be 4.57 or 5.13 gears.
