Back in the day , I sunk a bunch of money into my 12 bolt , super brute limited , Richmond gear's , alloy axle's , etc. With a 425 horse small block , auto tran's and 35x14.50 ground hawg's I used to spray that 12 bolts gut's out on a regular basis , (three times to be exact), I was hard on it though. Strong torque and big rubber don't mix very well for a 12 bolt. You might be ok with a stock big block and 35's as long as you don't beat on it but I wouldn't put any money into a 12 bolt with a big block and 35's myself , ( I learned the hard way , three times). 14 bolt is the way to go and they are cheap and easy to swap. As for the front the dana 60 is the way to go but they are not cheap and not as easy to find. I have had good luck with the 8 lug 44's and big rubber as long as you leave them open carrier. I was going though axle joints on this same truck for a while so I up graded to chromoly shafts and cmt joints, made my own axle truss, and then it was all good. By this time a dana 60 would have been nice but I didn't have one so I went the 44 route. The 44 will work well as long as you don't hammer it to hard off road. The only thing I ever broke on a 44 was axle joints which in turn took out the axle's as well, (and one time a housing , jumping), not the 44's fault just my stupidity.