If looking for an axle like mine you will have better luck finding one from a P30 chassis, used for step vans and RVs.
like this one http://good-times.webshots.com/photo/2024492560080251109VNDanJ
After measuring it it is almost the same as the 3500HD axle, same hubs brakes and spindles, but different steering linkage and perhaps a different width. It looks like it is better suited to narrowing for use in an AD big truck. The steering will even work with the original steering gear box, which is not the case with the 3500HD axle.

Eventually I'll narrow the P30 axle and swap it under my truck, but I will use a combination of the two steering linkages. The lower rear tie rod from the P30, and the crossover top front drag link from the 3500HD

I am still using the leaf spring suspension, but I will be adding air bags between the frame and axle in place of the bump stops. Right now my springs are 1" from bottoming out, without any sheet metal on yet, the air springs with an automatic leveling valve should improve the ride some over just adding more leafs.

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
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-