[Mike C]

I'm not trying to be mean and would like to help, but you didn't offer a lot of information up front and asked things that can be answered with Google or searching on the board. And can't be answered without the truck. (Which you did say upfront I might add!)

I learned all about rear axles with my own truck because I kept breaking them. And it was my transportation to and from college as well. I didn't have the luxury of having it down for long periods of time. But there were several instances that took extra time and required bumming rides from Austin to Lubbock and back. I was fortunate that the worst failure (broken timing chain at 252k miles) happened 5 miles from home.

I will still add that in your case the best choice will be to buy a complete axle with appropriate gears. The NP435 should be synchronized in all forward gears and 3.07 will work well I think. My '79 CJ5 has 3.54 gears and the 2.97 geared 3 speed and 33" tall tires and it does on OK job. You will have more weight but shorter tires I'm sure. And the good news is that 71-72 axles with 3.07 gears are not hard to find. If memory serves, the first gear in your trans is in the mid 4's.