If you wanted to convert to 4x4 you could use a front axle from a 73-87 1/2 ton 4x4
But the 73-87 3/4 ton was 8 lug. You can also have the rear axle you currently have drilled out to 5 lug cheaper and easier than anything else.
Personally I would use the 73-87 spindles, rotors, bearing hubs, backing plates ect and run 5 lug rims. Parts are cheap and easy to find and the 5 lug rims can be picked up from the donor truck that you get the front brake parts from.
