I'm going to add this here instead of starting my own thread - my steering problems, which were very similar to the ones in the OP's truck, have been solved. The truck was hard to keep straight at any kind of speed and had unpredictable sudden oversteer in turns. I replaced the radius rod bushings, wheel bearings, shocks, I-beam pivot bushings and steering linkage last year, which helped a little but did not fix the problem. Finally, I spent the money and the issue was solved by the installation of a Redhead steering gear and a quality alignment performed by someone with the right tools and knowledge to bend the twin I-beams correctly.

I've kept my early, between-the-I beams anti-roll bar, and according to the alignment shop my kingpins are fine. The alignment was a big piece of solving this, and I had to really hunt for an alignment shop that understood what was involved in working on these trucks. The laser computer alignment machine and the teenager running it at the local tire store is simply not the right answer. I found John Winn Alignment in Nashville TN - John is an old crumudgeon but knows his stuff and has the correct tools for bending the I-beams. No computers, no printouts. Now, my truck tracks straight down the road with no wander at any speed. The steering feels great! It doesn't drive like a new 2020 truck, but it does drive like a new 1974 truck.

I wanted to mention that I had an issue with the first box that Redhead sent out, but they stood behind their product and honored their warranty 100% with no hassle and no shipping cost to me. They were great to deal with.

 

Good report biasvoltage. Thanks for the added info.
Glad you got yours driving well again.

Paul