Thanks for the photos. They explain a lot.
The rear top and tilt hydraulic setup looks like a "do it yourself" job using a two spool valve like for a loader.
I do not suggest you get involved in redoing this setup.
You came to the forum looking for an answer to a simple question and unfortunately I do not think anyone knows for certain and further, depending upon the transmission the L4200 has, it may change things such as are there two fill ports or not.
The one aspect of this tractor that shouts out for attention is the condition of the hydraulic hoses.
A tiny pin hole in a hose under pressure can inject oil right though someone's skin.
With the valve and hoses located adjacent to the seat an operator is at serious risk. Every Kubota's Owners' manual contains cautions dealing with suspect hydraulic leaks and the key point is not to pass your hand over a suspected leak because of the risk of oil injection through the skin
Since you advised this tractor has a loader, the Tank line connected to the rear fill port could be redirected to tee into the loader valve Tank line. This may complicate things beyond where you want to be responsible.
I commend you for try to make life easier for your neighbor. He is lucky to have you living nearby.
Dave