First determine what the axles are rated, then the wheels and finally the tires.
Generally speaking on most half tons - the axles are overbuilt for the vehicle - so that it doesn't become a factor;
The wheels can support as much as 55psi - so I wouldn't exceed it with the tires.
The tires - 265/275's are probably the heaviest I would put on a half ton truck.
Capt AL - F/V Alice's Dream - Iceland
Unimog 5000L, 220hp BlueTec, 13sp, crew cab, Michelin 445/70R24 tires - 43 Jamco LQ trailer