Well, I've made some progress. I called the guy selling the 1050, and made a short trip to look at it. The tractor had been his grandfather's, and had run when it was last parked. Unfortunately, that was 20 years ago, and it had sat in a pole barn on a dirt floor. At some point, the seller's thieving cousin had removed the engine from the tractor.
I was able to take off the transmission cover, and the gears looked almost pristine. I had kind of negotiated a price by phone, and I bought it. The guy threw in what appears to be a functioning mower deck for the negotiated price. Good guy.
I drained the old oil out of the 1050, and took off the bottom cover, finding a thick coating of sludge. I extracted a broken bolt on the bottom cover, and cleaned out the gear box as best I could. I removed the donor transmission, including the wheels and tires (they were in better shape that the ones I had, and had chains), and re-installed the donor on the 900. Looking into the 900's gear box, there were multiple pieces of broken bronze bearing inside, that appeared to have come from the right side.
I'm still trying to decide if I want to reuse the transmission cover from the 1050, or drill some holes and use the original 900 cover that has much better paint.
I may be able to get this running tomorrow.
Edited by SgtMoonracer, September 03, 2015 - 10:03 PM.