1979 Silverado k10

[1976Scottsdale]

I just bought my new toy from a neighbor for $100.00. It has a 12 bolt posi rear and a 10 bolt front end, each has a 3.40 axle ratio on 33" tires, is this setup any good or not(also using a 350 engine, th350, np205). Only one problem that I have seen... the pinion seal is out on the rear end, no big deal, the problem is that where the passenger u bolts wrap around the differential assembly, the whole area around the bolts has saturation marks. This opens the possibility that the axle housing is cracked. If this should end up being the problem, can I weld it shut again, or do I need to get another axle?