Hey Bill, Have done all the stuff you have done and guess what?, mine still steers like crap too!! Currently thinking about doing the control arms, because that is about all that is left. Bout the only thing I could think of would be the Y to T conversion with the parts from a "99, seems like guy's are seeing some improvement, about $400 or so for the parts from Rockauto. Have you had an alignment done lately?
I am finding it is pretty hard to find a decent alignment shop that actually understands what they are doing other then giving it a tweak here and there and calling it "within factory specs".
I realize that with these solid axel's we don't have a whole lot of control, but that what we have is pretty important. I am finding that caster is pretty darn critical and often overlooked. Do a search here for the specs.
For the rest, well it is a Dodge truck, they didn't give us much to work with with this 1950's technology. It is to bad that we as consumers have to spend big$$ to improve what Dodge gave us and even at it's best can be described as "less crappy" It is such a disappointment to drive a different car or truck ( new Chevy 1500 drives real nice !!) and hop back in the Dodge and go "what the heck". I realize that other brands have problems too, but to me it is almost criminal how under designed and incapable this whole front suspension/. steering is for the weight of the Cummins.
Anyway, if you find something that works let me know, it might work for me!!