Adapters is another word for brackets in this case.
There are two types of spindles; drum or disc. There are three types of disc spindles; small bearing-short height, big bearing-short height, and big bearing-tall height. The small bearing-short height spindles are most disc brakes prior to 73. The big bearing-short height spindles are the ones called out in the mopar action article that most guys are after, which are found on 73-76 A and E body cars. The big bearing tall spindle was used on 73-80 B bodies. This same spindle was also found on all FJM body cars from 76-83. It will bolt up to any earlier car and in most cases will function just fine in most cases, but does slightly alter geometry. The geometry changes that result are so slight that you will probably never notice the difference.
If you want to keep your drum spindles, which are small bearing units btw, you can either buy a Wilwood kit that has the drum spindle brackets, bearings, hat, rotorss and calipers. These cost around $800-1000 depending on options. Other choice is you pick up the viper caliper adapter brackets for drum spindles, then use the bearing adapter for large bearing rotors, and viper calipers. This set up would run around $800-1000 depending on source of parts.