| The later supercharger with coating is the one to get ,provided the gear drive for the water pump is not damaged/worn ,
The coating is what is known as an abradeable coating ,ie it is designed to touch the casing and wear into size ,so it perfectly matches the outer with the rotor with a minimum gap.
This happens once the charger has got to its highest temperature and run for a few hundred miles .once set it should not change unless debris is passed through the charger or bearing surfaces alter-so a higher milage coated s/c would be better than a low mileage un-coated s/c all things being equal.
ps replace the oil before fitting | 
