Phil that is one hell of a weird problem, Is the engine clean? dirt and dust between the cooling fins could cause the overheating. Is the fuel tank mounted correctly (fuel outlet on the centerline of the plane) that could cause the mixture problem. You migh try rebuilding the carb, the only other thing i can think of if rebuilding the whole engine (bearings,ring,gaskets and complete carb rebuild). Im all for keeping old engines alive but you might just be better off to buy a new one, for the simple reason that your not dealing with these head aches.