You'll never find tapered bearings for your 3600 truck. A company called MBS used to make them but not anymore.
Original Equipment ball bearing is all that's availible.
Here's the spindle specs you asked for though:
http://chevy.oldcarmanualproject.com/chevyresto/55136.htm1953-1959 Chevy 3600, 3800 and 4100 used the same spindles
BTW- Timken and Federal Mogul/National part numbers are B45 outer and B46 for the inners.