You would probably have to measure yourself to find it to be honest. Plus 16.5s are really going to limit future tire purchases and if you ever have caliper issues you gonna grind things again and hope it works out. As good as a deal as it is now, in the long run its not cheaper. I would highly encourage you find the regular 17-18s or larger that came with the truck.
16.5s have less selection
many tire brands phased out that size rim fit for tires
week bead seats-low pressures and super easy to pop tires of the wheels if you air down or don't catch a leak
no clue on brakes so it sounds risky in general etc. even griding .5inch off a brake caliper etc. no telling how thick the cast is on those things now.