the factory shop manual covers the engines in great detail, and that is all I used when rebuilding my 2 216's, and the third one that I will pick up this weekend.
They are very basic engines, so just take digital pics along the way and there are plenty of people here that can help along the way.
If you prefer having them professionally rebuilt, which is fine, I would ask around. There are some antique tractor folks up that way that have a lot of knowledge about engines of this era, and many local tractor repair shops could handle the job, I would definately get references first and talk to the references, also look around their shop, It can be kind of dirty, but what you are looking for is if there are parts lying on every surface that is open. Valves, springs, etc.
You want them to be somewhat organized and not mistake any parts as they rebuild.(so maybe avoid the shops with 12 gazillion parts laying everywhere) Another route you can take, that My high school in North Carolina used to do, is that they would have a shop class in which for hire they would rebuild an engine/ or multiple engines.
the charge was very low. The teacher supervised the entire job and the students did the majority of the work.
In my junior year they rebuilt a inline diesel dump truck engine, and in my senior year a big block chevy motor for a pickup that they completely restored then sold to fund new tools and equipment for the shop.
Just some ideas, Jasper is also great as well.
