Since your only going to find a drum brake spindle on a 70-72 E body car, and a 72 and earlier B body car.
The difference between those, and the 73-76 A body Drum spindle is the diameter of the "shaft" where the inner wheel bearing is.
73-76 spindles use a larger diameter inner wheel bearing, and rotors used for the conversions, use modern day, low cost, easy to get, rotors, wether they are the standard 10.8 inch diameter, or the 11 3/4 inch rotors.
