Steering wander problem, opinions needed

[ScottH]

My 72 C20 has a steering wander issue that is really annoying.
I need to turn the wheel slightly to the right then slightly to the left, then repeat process in order to go straight down the road.

I checked the steering linkage and everything seems tight, replaced the idler arm and sway bar bushings. I also tried tighting the steering box but that seemed to make the problem worse.

Right now I'm thinking the box is worn but would appreciate any opinions, suggestions, or ideas to try before I replace the steering box.

Thanks.

Scott