Front axle questions gears and six to eoght lug swap

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Alright working on a 77 k10. Gonna be going 3/4 ton. I have 3 front 10 bolts. 2 0f the axles are 3:08's and 6 lug. The 8 lug axle is 3:73 but real rusty and has a leaking pinon seal.

are the caliper brackets bigger on the 3 / 4 ton?

Since the pinion seal is leaking am I going to have to set up my gears again? If so I will just swap them in the better housing.

Is gear setup really that hard on a ten bolt. It is something I want to learn and for the 200 plus it would cost to have it done I can pick up a decent mix.

Thanks for any input.