I agree that you don't need more width. I would discuss it with a Michelin dealer...not a bunch of kids at Walmart with all kind of certification patches. I have run these on a Jeep Cherokee parts runner. I would think that our parts runner gets about the same kind of use your pickup sees. Only a little more power. Its the last year of the 4 Liter 6.

http://www.michelinman.com/US/en/tires/products/defender.html

In Europe they have a 205 80R15, but I don't think they are available here. They stand up a little taller than the 70 aspect.

I now use a Jeep Cherokee with 16". As soon as the whatever name tires get a little more worn, I'm gonna buy Michelins for it. I have Michelins on my Town and Country as well as my 2015 3500HD.