Rear wheel studs on 71 c-10 question

[Jacksons Garage]

I am replacing the rear wheel studs on my 71 c-10 and am having difficulty locating replacement ones. Their shows only to be one replacement size available through all the usual vendors. The shoulder diameter or "knurl diameter" of the commonly, and only, listed replacement is in the .525 range. The studs that I currently have in my axles have a shoulder/knurl diameter of .622.

I am wondering if anyone has had this different size issue. I have even tried the Dorman site with no luck. I am also reasonably confident that it is the factory rear-end that came in the truck.

My factory stud dimensions are 1/2-20, Shoulder length of approx. 9/32", threaded length of approx. 1 1/8"

Any input is greatly appreciated

Thanks