Tire cupping

[87Skier]

I've got an 89 Suburban 3/4 ton 14 bolt rear, corporate dana44 front, and my front left tire is cupping on the outer edge. It has 230k miles. No lift and it is running the stock 235/85r16 tires.

I bought the truck last year, it had been passed around a few times, so no previous information on it. Had three new tires when I got it, with a 4th relatively new, but different style. All four tires are the same size.

Truck clunks from front end occasionally. I thought it was the sway bar so I replaced the bushings on the frame and didn't have any luck. I did the brakes on it last year, repacked and checked all bearings. Everything rotates smoothly, but I do get a slight vibration at highway speed. Not sure if is the bearing or the tire. Truck has very tight steering, no slack or wandering.

Any ideas of things to check or look at?

Thanks