okay looking at your stock sized tires (LT265/75R16) and if the tranny would stay in 3rd gear (1:1 ratio) your stock set up would have you spinning roughly 1,950 RPM to travel at 50 MPH. So looking figuring in your 37 inch tires here is a list of RPM related to the final drive ratio when driving in 3rd at 50 MPH
3.73 = 1694.3 RPM - What you have now
4.10 = 1862.3 RPM
4.30 = 1953.2 RPM - What I recommend
4.56 = 2071.3 RPM
4.88 = 2216.6 RPM
5.13 = 2330.2 RPM
5.38 = 2443.8 RPM
Here's the references for the front axle
http://www.reiderracing.com/dana60r.htm
and here's a link to
Randy's Ring and Pinion for you.
