I swapped the front (and rear) axles on my 2 ton, which would work the same as your 1.5 ton.
http://www.stovebolt.com/techtips/bigbolts/p30swap/The goal was to get disc brakes, with the axle swap came an obstacle (in my mind) of 2" more drop in the new axle. I had springs made with 2" of lift to correct for that.
If you wanted a "drop axle" for your 1.5 or 2 ton, and wanted disc brakes too, then you could do the same but keep the original springs. The bolt pattern on the new axles is the same as the old, hub diameter is larger but not a big problem.
Grigg
