[Mike C]

The NV4500 is neither an easy nor an inexpensive swap. The SM465 that your truck has really works in a wide range of circumstances. It's best to gear your truck to the 1:1 4th gear to get the rpm you want on the highway and take advantage of the low gear when you need it offroad. Even with 3.07 gears, the low range first gear in an SM465/NP205 truck is 39:1.

Compare that to the T150 in my 70 CJ5 where 3.54 gears a 2.97 first and 2:1 in the Dana 20 is only 21:1 low gear.

FWIW, except when needing to go super slow, get started with a trailer, etc. no need to use first. And the 3.5:1 second gear of the SM465 is WAY better than the jeeps stupidly geared 3 speed.