Do a little searching here.

For what model/year truck?

For AD 1 ton pickups I've found that a 14 bolt GM axle from a Cab and Chassis truck is a very close swap for the rear. I have one, have measured it, and I'm sure I can use it... but haven't gotten to it.

Front axle is not so easy, I've yet to find anything that swaps in nicely.
There are a couple different disc brake conversions folks have figured out and made, but nothing bolt on without fabrication first and nothing completely off the shelf.

Let us know what you learn and figure out.

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-