Some of the serpentine systems used a water pump that were known as reverse flow and / or reverse rotation. But not all the aftermarket manufacturers need to use a reversed water pump. You need to ask American Billet which pump you need. I don't know if any one here used one of their setups so maybe somebody might come along with knowledge of their systems.

You might also google their website ( assuming they have one) and see if they offer the info you're after.