I have been having the same debate with myself. Here are the tire sizes available in 15". In my case I am going with the largest tire diameter I can get due to 3.73 gears and a TH350 transmission. 265/75/15 which is basically a 30" tire. The only problem is there are limited 30-31" tires that are not mud grips or off road tread. And I want it to look like a slightly lowered street truck.
It really depends on what you are trying to do. I would first consider your drivetrain and figure out the diameter first. Then check that that style of tire is available.
https://www.tirerack.com/tires/sizes...sp?diameter=15