[WorkinLonghorn]

I think you should try it out with those gears and see if it might be an advantage to have low gearing when you are going up 410 to the Chinook pass or some other high altitude route.
One shouldn't be drive 75 in one of those. Just the gas consideration alone would warrant a speed of 55-60 IMO (not to mention the local speed laws).
Check those drum brakes out real well. I bought my current truck with a massive cab-over and rear overhanging camper. The first thing I did was put a new master cylinder, new wheel cylinders (or I "rebuilt" them, I can't remember), drums and shoes with new hardware. Also the old tires had plenty of tread but it was easy to see the deep cracking on each one. I had to replace them all.