After more checking on the backing plate clearance to U-bolts and springs I find:
Springs should be ~3/8" away from backing plate rim.
U-bolts should have 5/8" room between spring and depressed part of backing plate. (A max 5/8" u-bolt size may fit)
U-bolt nuts and axle saddle should have just enough room because of an extra depression in the backing plate.

I won't say that it'll fit, but it is extremely close and appears that it should, certainly worth a try.

I'll look into swapping for single wheel drum brakes and probably backing plates too.

I'm sure the disc brake conversion will fit.

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-