One issue that nobody has addressed is the diameter of the brake drums, particularly in the rear. 1-piece wheels designed for tubeless tires have a drop-center section to allow the tire bead to be pried over the rim, and some 3/4 ton brake drums are too big to allow the small-diameter part of the wheel to fit. If the drop-center section is spaced out far enough to clear the drum, the tread centerline is way too wide to fit under the fenders. 16.5" tubeless tires/rims are the same overall height as 15's, but the inside dimension of the rim is big enough to fit over the brake drums. Finding 15" wheels with the correct ID and offset might be difficult or impossible.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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