On the way back from my holiday trip, I noticed that my front tires are getting REAL noisy. Upon inspection at a truck stop, I noticed that the inside of the tire tread has a cupped shaped wear pattern. The tread lugs nearest to the frame are worn lower in an alternating pattern for the entire circumference of the tire. One block will have normal wear, the next will be worn down, the next normal and so on all the way around BOTH front tires. The rear is wearing normally and I didn't notice that much of a cup when the rear tires were on the front. Here's my truck/tire specs:

Original 235 Goodyears on stock rims always properly inflated (35 to 40psi depending on whether I'm towing or not.
Tires rotated once in it's 34,000 mile life so far and it's ready for another.
Suspension is 100% stock and untouched since new.
Truck steers, handles and drives perfectly with no pull to any direction.

WTF could this be? Caster, alignment, crappy tires?

 

Lack of tire rotation will cause cupping.You stated 34000 miles with one tire rotation,you would have been better off not rotating them at all.You should rotate your tires approx every 7500 miles for the best wear.

 

Check for a toeout condition,that could cause the treadwear you are discribing,it would also cause the truck to wander at highway speeds.