Just to add more to the mix, I've learned that there are 2.74 ratio first gear parts out there now (there are raging debates as to whether there were such OEM options for the 727).
With a modern low stall towing converter (non locking) it would make less heat and lower RPMs at cruise.
In addition, I need to check the tag on the Dana 70HD to see if it is one with a 5/8" pinion offset. If so, I might be able to put 3.73 gears in it. With those gears and my shorter 19.5 tires, first would be very similar to OEM and much lower highway rpm. Right now it is over 3400 at 70.

I should also put my old B3500's 4.1 gears in the parts section - free plus shipping.