Truck Repair: 1979 ford truck steering problem, radius arm bushings, wheel bearings

Question
Within one weekend I started to experience steering problems with my 1979 f350.  It was drifting badly and getting dangerous to drive.  I have changed many things trying to route out the problem, with minor success.  The truck now drives fine in a straight line, but is tricky on long curves (it tends to sway or initiate its own tighter turn when a slight amount of pressure to the steering wheel; sometimes it even refuses to respond to steering adjustments).  Here are the new parts that I have changed lately with mixed results:

steering box
centerlink (tie rods were tight)
kingpins
shocks
rear tires
alignment
radius arm bushings

What am I missing here?  I love this truck, but its more like work to drive it now...

Answer
Wow Culley,
You covered about everything.
I assume during the kingpin job, or the alignment, that the wheel bearings were checked.

The radius arms, I have seen break, but obviously yours are fine, since you changed the bushings.

Only other thing I can think of is the rear axle housing loose at the springs, and shifting. Try jacking it up by the frame, and not under the axle, and see if it is loose.

I might be tempted to get in another vehicle, and follow, watching the front end of this one while someone else drives it.