"I have the usual bump steer issues for the technology back then."
Maybe it was usual/normal on a 3600, but I have not had that problem on 48-55 1/2 ton Pickups, Panel, or Suburban.
What are your "usual bump steer issues"?
Have you replaced any worn front-end parts?
Have you adjusted/replaced all front-end parts?
Have you adjusted the alignment as described in the Shop Manual?
Have you adjusted the steering as described in the Shop Manual?
Might your tires be over-inflated?
On the Panel/Suburban a steering "damper" was stock equipment.
It can be easily added to a 3600.
