Longer wheel studs knurl diameter?

[spitfire980]

Hi Guys

My friend has got a 71 C10 in need of longer wheel studs on the rear

Its got drum brakes and im unsure of the knurl diameter

Summit lists them as:
0.535 in.
0.620 in.

While rockauto lists them:
0.687 in.
0.535 in.

From my research, the stock ones are 0.535 however im not sure if that differs between 67-70 to 71-72 and if the knurl diameter differs between drum or disc rears

If somebody can help me clarify

Thanks