This thread is/was about single wheel trucks....

A truck with dual wheels (almost) always uses the exact same wheels in all 6 positions, certainly true for the trucks we're talking about.
The front hub on a dual wheel truck has more offset to work with the wheels with more offset. Often same load capacity.

It's more about finding a rotor that works well and fits than it is about finding one of a particular size. I personally want as large a rotor as you can find and fit, nothing wrong with lots of braking ability. I'd at least want rotors and brakes from a similar size newer truck.

For more disc brake reading check out this thread, it is the most up to date
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=725027#Post725027
I'll admit that this whole subject is confusing and hard to follow and that I haven't figured out a perfect "kit" for big truck disc brake swaps. I among others have been working in this for a while and there is more than one way to do it, read some of the other recent threads on the subject too.

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-