What are you trying to do?
I ask because the slow gears in the rear axle might be the biggest problem (usually are) and throwing transmissions at it won't make enough difference. Swapping rear axle and possibly transmission too might be the answer... depending on your goals.

The right NV4500 and or with the right adapter can bolt up, it's a good and common swap. Good choice for a full size truck. The T5 is a good choice for a small truck.
bigbadswingdaddy knows his stuff and I'm sure has detailed answers for you.

One of many threads on the subject
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=620037

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-