I have a 2004 f-350 crew cab dually hauling an arctic fox camper. i just got new michellin tires which have a load range E, tire says max psi is 80lbs cold. could someone recommend what pressure the front and rear tires should be at?

 

That F350 should have come with at least LR E tires from the factory. If they did, use the pressure on the door. If they did not, I would check with Michelin, making sure to let them know your specifics, including the real weight of the vehicle including the camper. I would suspect, at least a bare minimum of 65, but I am not familiar with what is normal for an F350, only F150s.