GM started building 1/2 tons with 5 bolt lugs on the 71 model. For the rear end, it depends on which model you have. If yours is the heavy half with a floating axle, you will need to replace the differential. If you have the standard rear end, you can swap out the axles only. A lot of the 1/2 tons had 3.73 gears.


Fred
52 3600
69 C-10