That's a good list. Being 40 years old, many of those points will need attention.
Pump relief valves can be rebuilt. There is a guy on ebay who does it for reasonable cost. You have manual valves--that is, the little buttons on top need to be pushed down to allow you to move the tractor when the engine is not running. Auto valves are available that do not require the button to be pushed down--they don't have the button. New valves are $$ but sometimes the expedient solution.
There are several documents in the technical library you should look at, specifically about the hydro--how it works, hydro lurch, trunnion repairs, etc. Download the service manual if you don't already have it. There is a very good section on the hydro.
There is no axle pivot bushing, just a pin. (well there are a couple sleeves welded to the support channel, that the pin rides in, but I wouldn't call them bushings. Anyway, they are not replaceable, at least not easily.)
A shop will charge you $800-$1000 or more to rebuild your engine. If you tear it down, take the block to a shop to have it bored ($200) and buy a kit ($115) to rebuild it, you'll save the difference. And you can repaint it in the process. Just a thought. If it's not smoking badly or blowing oil, and runs OK, you might postpone that until a future date. Just remove the head, clean it up, new head gasket and call it good.
Depending on how much you want to invest in the tractor you may decide to limit the scope. You can easily spend $3000-$4000 if you do everything including new tires and an engine rebuild. Your tractor will be worth less than $1000 when you are done, so consider that.
__________________
|