Welcome aboard. I can't answer but one of your questions, the differential. Yes, it is very reliable, provided it has never been run dry. I don't know what gears you have, I assume 4.57 or 5.14. You can easily go to a 4.10 with a pumpkin swap from a 12 bolt up to 72. Your only other option is to swap for a 14 bolt, which are available in 3.72, there are even a few 3.42.


Fred
52 3600
69 C-10