Lower ball joint prices

For my 65 Dart, I bought Duralast lower ball joints ~$60 ea at Autozone w/ free shipping. I reused the uppers since they seem fine, and put new polyurethane boots on both.

Originally, I bought lowers ~$30 ea at RockAuto (Mevatech), but ones listed for disk brakes. I had read several places that disk and drum ball joints were the same, other than the disk ones were more rugged. Since 1/2 the price, I followed that path. When I began to install a year later (its dragging), I found not true. The disk ones not only have larger bolt holes, the bolt spacing is wider. A guy on ebay was recently selling a K-H disk brake setup and suggested one could just drill out their drum ball joints for the bigger bolts. Nope. I'll try to sell my disk ones, along with other "didn't fit" parts when done.