Those 20" P tires are probably max rated at 44 or 51 psi. Never over pressure a tire but I would use max sidewall pressures especially in the rear tires as its carrying all the load.
I pull a 10k bumper pull car hauler with a 1500 crew cab 4wd chevy riding on P265/70-17 " tires. The bigger load is a 7400 lb blue tractor with a cab which adds 1000-1100 lbs on the trucks rear axle depending where the tractor is placed.
When towing or carrying loads I pump the trucks rear tires to 44 psi max sidewall pressure and 35-38 psi in the front. The trucks front axle doesn't change weight so I have no need to use different pressures.
Having owned several 1/2 ton trucks since the late '50s, I've tried using LT D and E but always went back to a P tire...or a C load range if I can find them.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides
