Personally, if I had a M3W I'd be looking at swapping out the S&S and fitting a more mainstream Harley motor.
No way would I change the engine type. The V2-MTW is sure to become a collector's item. Then the original engine also belongs in the car.
I'm sure there will be remanufacturing parts when parts from the S&S factory are no longer available. Perhaps initiated by the Morgan Threewheeler Club?
I drive a 1946 Indian Chief and every engine and transmission part is available as a replacement for this engine.