I found my problem. The rack guide (the part that pushes the rack against the pinion), was deformed/burred somehow and was binding in the housing. I did adjust the preload on the spring, but the rack guide wasn't able to do it's job, so that's why it made no difference. The car was beat on by some farm kids for a few years of it's life, so I can only imagine the damage to the rack somehow involved a cow and a big ditch.
I straightened the edges of the seat and rack guide out, and smoothed out the bore in the rack housing with some stainless steel wool and put it back together, making sure it was sliding freely in the guide bore, and the rack is slop free.
Not sure if this is an isolated thing, or if this might be the solution for anyone else. It's not hard to check, just need some oddball tools. I made the tool to turn the rack adjuster out of a big bolt with a nut welded to it, and I already had the large wrench required to loosen the locknut. Also need a small mirror, a magnet, and something to pull the guide out if it's stuck like mine was. I managed with a screwdriver and a hooked pick.
At least it was just something stupid and not something really stupid. :kaboom:
Now I can properly blow my insurance check on better brakes, or wheels, or that lightweight hood I've been drooling over. :naughty: