Fordson model F

http://www.thefordsonhouse.com/p-fordson.html

If the engine is stuck, how do you know you need new pistons? The old ones may be OK if you're careful getting them unstuck. Look through the archives on this site for a variety of ways to get an engine unstuck. Lots of different recipes -- biggest trouble is deciding which one to use. Most important thing to have when working on a stuck engine is patience -- let things sit for a while (maybe even a few weeks) to allow your chemicals/oil/whatever to work.

The site that HammerHead posted is a good source for all kinds of Fordson parts, but you'd be wise to shop around, in order to get the best price.

If you need piston rings, try Lang's Old Car Parts in Winchendon, Massachusetts Link