[flatheadmurre]

Problem is that a narrower belt can´t handle the same amount of power and not wear out faster.
And you need enought length of the belt to make contact with the pulley.
I´ve seen setups where you ad PS and AC on top which makes the belt barely touch the waterpump...not the best solution.
Making a custom widebelt pulley for the PS pump is one way of solving it...