If you're that concerned about load, several manufacturers offer 19.5" wheels with the 8-lug bolt circle of the OEM 17s. That would allow you to run 19.5 tires with higher load ratings. Otherwise, you're not going to find higher rated 17" wheels unless you custom order them. Otherwise, I agree with Cummins12V98 - the 4 rear OEM tires and wheels are rated well above what the rear GAWR allows (11,340 pounds to be exact for the 235/80 tires - rear GAWR is currently 9750 pounds).