Underdrive Crank Pulley.

It will slow all the pulleys down 52%....which seems pretty considerably to me? Most pulley kits I've seen slow them down about half that amount? In any case, you can still source a smaller alternator pulley to speed it up and bring charging levels close to normal again. Unless you're experiencing overheating issues, I wouldn't really worry much about swapping out the waterpump pulley.