One of the disadvantages to the tapered bears is that you will have trouble running disc brakes on the rear axle. The preload on the tapered bearings allow the axles to move slightly. I had trouble with this years ago. If the brake calipers stick sliding for any reason then it will grind one side down fast and drag.
Agreed. And also the calipers and rotors become your safety cushion for side load and failure. I believe straight cut bearings should be used with disc. I never had rear disc on a pre 72 car?
