Yes, you picked a tough one. I may have to continue my reply a little later today, but I'll start now. And you've done a good job tracking down some info already. Here's a picture from the Ford truck parts book.
![](http://i1235.photobucket.com/albums/ff437/red0wl/Ford%20truck%20power%20steering%20rs%20arrow.jpg)
There are two of the same bushings on the big bracket, I have an arrow pointing to them on the left. They are Ford part number EAD-33640-A. There is one different bushing on the smaller bracket in the right side of the picture with the right arrow. Ford made a change in the bushing during production - initially it was part number EAD-33460-A, then changed to C7TZ-3D712-A later. I was hoping the parts book might give dimensions or an industry interchange number, but unfortunately it doesn't. I don't know what changed in that second bushing that required a new part number. And as you are already aware, these parts are long obsolete from Ford. I tried some Google searching with the part numbers, it doesn't look like you are the only person looking. I also tried a couple obsolete part companies, no luck there either. It looks like those bushings also were used on various early Thunderbirds, so I'm guessing all the old stock was snapped up by restorers long ago. I have to go right now ,sorry, but I'll come back to this a little later.