Weight of ouer F350 single rear tyers 1680lb front 2350lb. Tyers Michelin LTX A/T 275/65 R20 rated at 3750lb at 80 psi. Ford recommends 65lb front 80lb rear. According to michelins load and inflation ...
That's about right I'd say. Being a 250, 2012 model you won't get away from the tpms light on your dash with the lower pressures unless you've had the pressure thresholds adjusted. I used to run 50/40 in my 2013 F250 gasser totally empty. Lower in the winter when it was all ice n snow. Just make sure you air up before loading er down for a trip!