Hi MS,
Biggest issue might be what grsmnky is referring to. I'll get back to this below.
I have a '92 3930, with a 3 cylinder 3.147 L diesel, non-turbo. I like the engine, so far. Bought used, with about 1400 hours on it. In the 70's and 80's, my uncle's ran Ford tractors, had great service from them - unfortunately, both my uncle's and the tractors are no longer around, so I can't quote models/engines.
I like Fords, but was open to other brands when I went shopping for used tractors a few years ago. Did bid on a Case before I got this 3930, but dropped out of the bidding. The price went crazy high (IMO) for the hours and condition of that Case. Just sayin', I'm open to considering other brands for the right price.
If Soundguy sees this, he may chime in, if not, try PMing him - I might be wrong, but there is a good chance that he may have direct experience with the engine you are looking at.
Tractor has been sitting a lot, over all those years. Test drive it, if everything critical works, have somebody that knows diesels well check the engine (compression). Have a good look at the fluids, if the anti-freeze looks like oatmeal and/or U-haul orange colour - your call if you pass, or knock the offer down.
I don't know you, so don't take this the wrong way, but plan on changing ALL fluids right away. Antifreeze will be shot, and all oils will be loaded with moisture.
As a tractor mechanic commented to me "2 things many people don't service on tractors - Antifreeze and Hydraulic fluid". These two are often neglected, even on tractors that get other items serviced.
I can't tell from your post if you are new to diesels period. Read up on fuel treatment and storage tips if you are new to diesel - critical anywhere, but esp. if you have to deal with cold weather, and want to use your tractor before Spring !
Please let us know what more you find out, and what you decide.
Rgds, D.