It appears to me most of the fastener kits are one proved by amkproducts.com and the others vendors are resellers.
Below is a link to the 1972 Chevy C10 kit.
https://www.amkproducts.com/master-k...s&element=Body
The master kit has 469 pieces and costs $275
I purchased my kit from AMK and it was pretty darn good. I did find a few mistakes and they promised to fix them in future kits.
The fact they are not located in China was appreciated as was they actually answered my email.
Quote from their site;
"Chevrolet is as American as apple pie. We know that at AMK and pledge to produce a minimum of 80% of the fasteners used to make our Chevrolet fastener kits right here in America, currently we are exceeding 82% USA made content."
Some times the resellers are less expensive than getting directly from the manufacture. I'm not sure in this case. However, the web site does give good pictures and explanation of what is in each kit which I doubt in included in the resellers web sites.
cheers.