There should still be some dottering old fools left around.....but they would certainly be old...like really old....almost as old as time itself.
The transition from a 300 to a piston Medium would not be that big a jump I should think....as it is muscle memory with the left hand and arm...and feet.
If the Huey guys up at Wesham are practicing manual governor much....they would be good candidates as well. Neil would be a good one to talk to.