Hey Jeff,
Essex is a nice place to be. Great ship building museum and boat hardware junk shops. The thing that I am finding is that the same tire desigbation, say 6.50, may differ 2" in diameter between brands.
I would like to run as tall a tire as I can get away with for road speed but don't want the truck to look silly. So I'm guessing now with your input that 8.25 would work. The ones available today are 39 1/2" tall ! What is the height of yours ?