I just went through your pix, and I noticed a couple of things. 1, your rear differential is a 2 speed, nt the single. That means you can have one of 2 different ratio gearsets. It's either a 5.83/7.95 or a 6.40/8.72. If it's the 5.83/7.95, that would be very good, as the high range would get you a bit more top end, especially with that Cummins you plant to use and an overdrive trans. Plus, you get the benefit of a low gear for pulling if necessary.
The other thing I noticed is that the original engine is still in place. Whatever you do, don't scrap it! That engine is the very desireable 261. Even if you don't use it, you could sell it for some extra cash.
