How many lugs on your wheels? 6? 8? other?
If your truck has the 1/2 ton rear, 3.90 and 3.38 gears are about the only options. There was a very rare 4.11 gear set, but it is not likely to be in your axle.
3/4 ton trucks likely have a 4.57:1 ratio
1 ton trucks likely have 5.14:1 ratio.
When you say used to be 4wd, does that mean a NAPCO 4wd, or something that may have been cobbled together on a farm?
