[bronze 72 super]

The drums you bought are for 1970 and older1/2 in. stud, '71-72 went to 9/16 stud. The "chain" parts store are terrible at finding the correct parts for older trucks and cars. I use only a independent store that uses a wide variety of parts books, more so than "chain" stores. The drums I bought were the correct ones for a '71-72 truck. Drilling them out is a unnecessary step that could have been avoided, if that store did it's research a bit more thorough. Also that retainer hole has to be countersunk, for the flush screw that goes in. Best to find someone with a drill press and the proper countersink.