Yep, no problemo.
If you have a GPS you can also get the tire size perfect with a simple formula.
Truck odometer divided by GPS odometer and that multiplied by the current tire size entered in the programmer. The answer is what you enter into the gryphon.
If you have pegasus there is a nifty little tool called "Gear ratio calculator". Just put in the current tire size (ex 255/70-17) and eastimated tire squish and you can get really close to the actual tire size.