Here I is Woog!
Rance,
Everyone else has covered this well. I have a '66 stepside (that hasn't been driven in 6+ months, sadly enough) and I once had a 230/3 speed/3.73 gear combo. With my 235/70R15s its top cruising speed on the interstate was 65 mph.
So I built a 292 and kept the same wheels/tires and rear end gearing, but added a 4 speed manual stick tranny, with 4th gear being overdrive. Now the truck turns about 1900 rpms at 60. And when I want to jump on the interstate, I have no trouble doing extended trips at 80 mph with the fast lane traffic, as the overdrive keeps the rpms at only 2600.
My advice would be to drop in a 4 or 5 speed overdrive and be done with it. The "taller tires" solution is not going to take your truck from being a "high rpm/low speed" beast to an easy interstate cruiser.
-ftyler
