The NV4500 transmission may be a better option. It comes with a pretty low 1st gear of about 5.61:1. It has an Overdrive of .73:1. These transmissions are found in both 3/4 and 1 ton Dodge and Chevy trucks. They are considered to be bulletproof.

You need to think about speedo hookup. Do you have a 2 speed rear axle? If not, your speedo cable prolly goes to the transmission. Many of the newer transmissions are set up for electronic speedos. If you plan to use your mechanical one, this could be an issue.

If interested in the NV4500, look for a unit from a 1992-1997 Dodge 2wd 2500 or 3500 series truck. You probably won't want the unit from a cummins diesel engine because it has a larger input shaft and won't work with your stock clutch.

Why the 92-97 dodge unit? The 92-97 dodge units are the only version of this transmision that come with provisions for a mechanical speedometer. The input shaft is also 1 inch longer than the Chevy version. This allows you to have an adapter plate made to go between the bellhousing and transmission and allows you to use your stock clutch set up. The input shaft should be the same as your stock tranny... 10 spline 1 1/8 diameter.

Hope this helps.