Pretty big difference between a Jeep and a 3/4 ton full sized pickup.
Can you even get 15" wheels with the 8 lug bolts?
I would do the 17" wheels because the 15" tires are getting harder to find, and that is not going to improve as time rolls on. In a few more years, I suspect you will likely only have one or two brands and sizes of 15" tires to choose from. Gene