It's a known problem that has been resolved by Morgan on later M3W's. They repositioned the mounting on the chassis, the earlier cars like yours are on the engine. There are better quality rubber bobbins (anti vibration mounts) available that reduce the wear but basically they are reduced to powder with vibration, as you have found. It's not an oil cooler by the way but a rectifier/voltage regulator unit, hence the wires going to it rather than oil pipes.
