To start with I'm in Australia and I've had an F10 for over 30 years now but started to get horrible crunching feeling from the steering and play that couldn't be adjusted out. I finally removed the steering box and found the lower ball/thrust bearing had collapsed rendering it un-usable as the inner race is part of the shaft. After searching for several months I found an F10 at wrecker yard not to far from home and they wanted $140 for it if I removed it so I purchased it only to find it slightly different to my one. My original had a bent drop arm and this one had a straight drop arm but it wouldn't fit as it put the drag link to close to the chassis. The straight arm box is for sale if anyone wants it but it meant I had to fix my box.
After a lot of head scratching I decided it would be possible with some rather difficult maching to turn both ends of the input shaft back to parallel and fit tapered roller bearing and the housing needed maching as well. The maching was difficult as the shaft is very hard bearing steel but with ceramic tooling I got there. Reassembled the box after shimming to what I thought would work and back in the car and the steering is now back to normal. Normal isn't very good but at least no crunching and no play.