I'm going to ask my machine shop guy how accurate his 30t press is, and if it's good enough, I'll press it on to 25 with that. If not, I'll just press it on to 20 and call it a day.

Some more progress. Very enjoyable when parts are reassembled with new hardware and chased threads, everything lubed and shinied up. Left-side final and brake assembly reinstalled with new bearings, seals, hardware, etc. I used caulk instead of cork, because a) it rhymes, and b) it'll probably seal better. Rolls very smoothly. This side has new clutch hubs and plates from General Gear. The steering lever rebound springs were frozen up so they're all free now and working as expected. Speedi-sleeve on the pivot shaft for the seal, E-Z Loks in the final housing for the fender. Welded a new thread on the gear lever so I fit a new knob.
Tested out the clutch after fitting the left side - very satisfying. The clutch lever has a stop adjustment on it, that I adjusted to limit lever travel to just before the clutch bottoms out on the springs, which I presume is close to what it needs. It has 3" of free play when engaged. Brake works like new. New bellows seal.
I'll put the unrefurbished left track frame on next week so I can turn the tractor around and refurbish the right steering. I'm going to get my guy to make a couple of pins that are a snug but not tight fit in the rails so I can easily put the tracks on and off while I dick around with the track frames. I was excited because I thought I was buying the old-style master pins with the plugs 2F2565 from Blumaq but they turned out to be the regular and current interference fit pins.

I'm assuming I'll need to adjust the rails but of course, the threads on that long bolt and the nut are frozen / rusted / wasted. Don't really want to replace a whole bunch of stuff on this frame if I can find better ones that are all rusted out but may have to. Presumably those bolts are still available?

Jeff, bellows seal is 2H1542, obtainable from General Gear.

I made some progress today. I've had this unit for years and finally got to drive it today, to test out the new steering and brake on the left side. Even though it's a tiny tractor, I was really surprised at how easy the steering is when it's all brand-new, and how the tractor just turns effortlessy (admittedly on asphalt so not a real test). I also lucked into getting the left side track adjuster to move, so I took it all off, cleaned up the threads and anti-seized it, and now it adjusts like a silk glove.

Here's a video of me grinning like a Cheshire cat as I drove it out of the garage for the first time to turn it around. Enjoy the old-timey seating arrangement...

Now, to do the right side final/steering/brake.

Those are welding gloves because I had to remove the GP-special exhaust foghorn arrangement after getting it started.

Now that I remember, some other items made it in to production as well:
- replaced the old locking tab on the pony pinion so the nut doesn't undo itself anymore. Was able to let it run for five minutes by itself turning the main under compression. Temp gauge got pretty close to operating temp while running under pony but didn't register a thing under the main engine running. It noticed some slobber so I'll try not to run it too much until I can get it into a field to work it
- new fan shroud from Bert (657) and it looks good.
- freed up the steering lever controls and rebound springs - smooth now
- fitted new plugs into the master pin on the left side after shining everything up. Together with the now-working track adjuster, it'll be simple to get the left track off again - a) I put it on the wrong way, and b) I still have some refurb to do on the left track frame before I can reattach the 2S blade mounts

Still have a lot to do:
- right side steering/final bearings/brake
- broken bolts too numerous to count
- right side track frame refurb
- electrical wiring and gauge set up
- battery box mount and cabling
- main fuel tank and plumbing
- 2S blade mount (blade has been refurbed but I've held off the mounts until I get the tractor down to the machine shop so that can fix it in situ so we know that it will fit
- D2 Hyster winch and hitch.

Still, it feels like progress to have it move under its own steam finally

Heh, yeah those tracks are basically slicks. I "had" to turn it around so that I can fix the other final. That's my story and I'm sticking to it!