why not just use a stock ford dist and spend those dollars somewhere else?
I haven't run any numbers on the revs but IIRC some of my earlier trucks did cruise at 33oo at 75mph with the trailer 373 gear and the 16.5 truck wheels/tires

just driving around with 3.25 gears you won't get in into a hp range on the street at the speeds you'll get to so you need to do gears and cubes
that 110 octane will cost you about $15 per gallon plus shipping unless you have a dirt track near you that has it