Tires: Uneven wear on K1500, stiff suspension, carrying capacity

Question
I have a '92 GMC K1500 that is showing uneven wear on all four tires. The tires are wearing on the inner and outer edges like the tire pressure is too low. Door placard calls for LT225/75r16,C at 50PSI and I am currently running P245/70r16 at 38PSI. Is this simply a matter of needing more air pressure or do I need to stick with LT tires, even at the larger size?

Answer
Sean

An LT225/75R16 at 50 psi has a load carrying capacity of 1940#.

A P245/70R16 has a maximum load carrying capacity of 1903# at 35 psi.

While I normally don't advocate the use of P metric tires in place of LT metric tires (usually because of load carrying capacity reasons), this appears to be OK.

I suspect that because a 4X4 has a fairly stiff suspension, that the softer tires are doing most of the work that is normally done by the suspension and the result is wear on the shoulders.

I also suspect returning to LT metric tire would probably help.