I am just wondering about why you are at your top speed at 65 mph? I have run gear calcs for the stock 2003 VW Golf my folks have and my Toyota pickup as I want it configured when I do this engine swap. The golf has .76 5th gear, 3.39:1 final drive and 25" tall tires which comes out to 2251rpm at 65 mph. My Toyota pickup has .85 5th gear, 4.1:1 final drive and will have 33" tires which gives me 2306 rpm at 65 or 55rpms more then the stock golf at the same speed. If you run 32" tires on the same truck it's 2379rpm at 65 or 128 more rpms then the stock golf. And with 31" tires it's 2455 at 65 or 204 more rpms then the stock golf. None of which are so much higher then the golf that I would be even slightly worried about it. I have driven my folks golf across Nevada and Utah at close to 100 mph and 3400+/- rpms and still knocked down about 38 mpg. Unless you have really small tires on you truck I would not worry about changing the gear ratios. Besides that you don't really need to be driving a truck at 80 mph, the areo drag becomes so great your MPG will really suffer.
Anyway, that's my $.02.
Jaysin