Dan, I would suggest doing some reading on the off road forums. I think you'll find that most of the guys will say that somewhat lower pressures will help you avoid rock punctures.
EDIT: My feeling is there is no situation, at all, for those tires on that truck where you would run 80 psi. Or even 60 to 70. The truck just can't carry that much load ( weight ).
I also have a F350 dually with load range E ( 80 psi max ) tires, and even with the 14K pound horse trailer on the back, I don't run 80 psi ( but, it's got four tires in the back, but still, there is more weight on the back axle alone than what your Tacoma, or my Frontier weighs in total. I'm usually at 5600 to 5800 on the rear axle ) And at that I run 60 in the rears and 70 in the fronts.
