The nuts you had are called "Marsden" nuts http://www.lok-mor.com/mar-loc.html
I think NAPA does list them as I saw pictures in the catalog a month and a half ago. And I've seen them on original Chevy trucks. I've got some wheel adapters that were installed early on if not when new, and they used Marsden nuts for lug nuts and not very likely they ever came off or were replaced.

Have you looked in a 60's parts manual to see what was used when the truck was new?
We've both/all been guessing at it so far.

I looked in the 29-54 parts manual (I don't have a newer one for small trucks)
Page 371, section 5.820
"Ring, Rear wheel hub clamp"
Part number 3680931 (fits 1 ton)

I did not look for the nuts, but can later this evening. Did notice a nice chart of studs with dimensions and part numbers.

Part of what you may run into is you have 1/2" studs, and later stuff has 9/16" studs.
Did you investigate upsizing to 9/16" or would the hubs need to be bored larger to fit the available studs (which is an option)?

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-