Incorrect wheel hub

[gmc4x4can]

Need some help here. Switching to discs on my 70 k10. Truck came with the parts uninstalled so now im installing them since one of the drum hubs is done. Problem I found with one of the new hubs is the stud holes were drilled to large at some point on one hub, so i cant get engagement when i press the studs in . I went to the local auto yard and they had a 76 blazer hub that supposedly is interchangeable that lookd exactly the same so I bought it. I got the races out of my damaged one and found the inner race to have a smaller OD than the blazer hub, and it has a lip so it doesn't press in as far on my damaged hub. First and third pics are damaged hub, second and fourth are 76 blazer hub.

Do you think my hub is not a 71-77 or is this blazer hub not really a 76? If nothing else is there a way to fix my stud holes?