The 80psi that it says is the maximum manufacturer recommended pressure for that tire, being that it's a Load Range E. If you have a 1500 don't run 80. I've been running 40 on my 35s for two years with no issues. I would say between 35-40 on that size, pending the truck.
I know this thread is old, but since it was resurrected, for future reference, this is a Tire Load Inflation Table from Toyo, but it applies to all brands of tires, (you can get the same information from the DOT, this was just easier to find).
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