Hello Dave
There was some discussion on spindle size recently. Do a search here for spindle. The years 39-40-41 all made changes to the spindle. It takes some time in a parts manual. I believe you can change your spindle to 1/2 ton BUT only with a 40 1/2 ton. A 41-50 axle will bolt in your truck without any changes, and makes parts location easier.
There is an outfit here in Wa that makes the parts necessary to switch to disk brakes with 6 lugs. Buffalo Products or Ent.
