The tire manufacturer does not publish specs because the application will vary so much. The only thing they specify are the maximum safe operating parameters. If I put the same exact 35" tires on my TJ Wrangler as on my Super Duty, then the proper level of inflation is going to differ wildly between them, especially if I'm pulling 15,000 pounds worth of gooseneck behind me.

And the story about inflation levels having no affect on tire wear is silly. So much conjecture and misinformation floating around about such simple stuff. I hadn't realized so many people rationalized this kind of thing so hard.

If you're really want a low-tech way of finding the "correct" inflation levels with non-standard tires, try the chalk test: park the truck where it can drive straight down the road, take some sidewalk chalk and draw some lines across the tread (or color them in if you're really bored), and then drive the truck straight down the road for a couple of houses or even a block or two. Get out and see what it looks like. If the edges are rubbed off but the center is still there, it's under-inflated. If the center is gone but the edges remain, then it's overinflated. If you consistently get the entire line erased in just a short straight drive, then you're good to go. This will change under extreme load, of course.