Well, here's the latest (and possibly last) update.
I finally got the thing back together yesterday, and it started up pretty much right away, but...now it has a slight knock to it and it's definitely burning oil (constant light blue smoke coming out of the stack). Didn't do either prior to it quitting on me back in December. Took it out and started to use it to finish moving some gravel, and bogged it down and it quit. Seemed like it just didn't have as much power, but I really didn't get to use it enough to tell for sure. When I tried to restart it, it cranked a lot slower and wouldn't restart right away. I was letting it cool down to restart when I noticed smoke or steam rising from around the starter. Got off to look and saw two things; water dripping from a VERY small hose (maybe 1/4", the smallest replacement I could get was 5/16" transmission cooler line) which evidently runs from the block over to a drain petcock and another hose from the radiator. The second thing I saw was what looked like a little fire down lower on the engine, which turned out to be the main positive wire from the battery shorting out on the frame! No wonder the starter didn't want to turn very fast. By the time I went to AutoZone and back, I had other things to do last night. So this afternoon I came home a little early and worked on it some more, putting the new hose and new battery cable on (with a protector over it this time). I ran some engine flush and radiator flush through the engine, and changed the oil and filter. I put some Rislone Ring Restorer in it, not that I think that's going to do a world of good, but at this point I don't figure it could hurt. It's still noisier than it was, and smokes some, but it starts right up. I guess I'll just run it like this and see what happens. If the taxes turn out right, I may still be looking at a new, larger HP tractor. I hate to get rid of or give up on this one, but I've got too much stuff I need to do and not enough time as it is.
I sure appreciate everyone's help on this-without you guys, it wouldn't be running at all. Who knows-maybe it'll run from now to eternity and just use a little oil and be a little noisy.
Thanks again!