I Have had two fifth wheel trailers ( one Teton and now a Mobil Suite) which came with Good Year Unisteel G614 RST. These have a load rating "G" of 3750 # in LT 235/85R16. They are a very high quality and will handle a heavy load under all conditions. I consider them a very safe tire on the express ways. I typically run the posted speed limit as not to hold up traffic. They are on the expensive side but would not look for anything of lesser quality.
Rovol
2008 Dodge RAM 3500 Laramie Quad Cab 4X2
6. 7 Liter Cummins (R) Turbo Diesel Engine, 6 -Speed Automatic 68RFE Transmission, 3. 73 Anti-Spin Differential, Brilliant White, ISSPRO Gauges, Transfer Flow Fuel Tank, PullRite #20,500 Super 5th Hitch, Line-X, XTRA Bed liner , Hayes Genesis brake controller, PML Deep Transmission Pan, Custom Graphics, Pull a Mobile Suites Fifth Wheel.