5.9L Cummins - '78 Bronco project

I'm currently swapping a 1991 12V 5.9L Cummins into my 1978 Bronco. I am using a 460 C6 with adapter from fordcummins.com, the C6 converter and Cummins flexplate. (adapter to bolt them up from fordcummins.com, too), along with the original NP205 bulletproof transfer case mated to the C6. The motor mounts(yes, also bought from the same place) position the 5.9L 3" back, which means the transfer case and transmission are also back 3" from stock. With the 6" suspension lift on my truck, that 3" reposition should be perfect with the stock driveshaft.
I am using the dodge truck radiator, along with dodge steering pump and alternator.
The stock 5.9L motor is 215 hp and a nasty 440 ft/lbs of torque at 1600.
A 4" turbo downpipe and no muffler, with 4" pipe running out under the passenger side door should work good.I'm going to advance the pump timing and such, of course, so the torque will likely be 500 ft/lbs or more.

I'm going to try the stock 3.50 gears and see how the mileage is, it will cruise at 55mph @ 2000 rpm. I'd prefer it was at 1500-1600 rpm, I might need to swap in some 3.00 gears, we'll see. It would be ideal to cruise right at the peak torque rpm,(1600) and 500 ft/lbs will definitely climb hills nicely.  

The truck has 9" of lift, (6 susp. + 3 body) 35" BFG tires, 9" trac loc rear, D44 trac loc front. Just bought it a few months ago.