Tapered bearings for 3600 or any pre-59 GM truck are unobtainable. I have a set of tapered bearings made by MBS out of Japan. Unfortunately they aren't made anymore. A tsunami followed by a nuclear meltdown put a cramp in their manufacturing. To be honest, they didn't fit that well to begin with. The outer were ok, but the inner needed some massage work. I had to emery clothe the Dickens out of the spindle to get them to fit. Then the seal. It rides on the inner barrel of the bearing, well I had to use machine bushings for clearance so it didn't tear up the seal.
So, in conclusion, the oe style ball bearings are more than adequate. The 3600, 3800, and 4100 trucks use the same bearings, so they 're plenty stout.
