First of all, a REVERSE FLOW water pump doesnt look like a regular Chevy pump. The dstributor is on the front of a reverse flow engine.

A REVERSE ROTATION pump looks exactly like a regular water pump except that the impeller is shaped to pump water when the pulley is turned the opposite way.

OK, what is a reverse rotation engine? Any small block that had a serpentine belt (not a v belt) is reverse rotation. If your engine was originally equipped with a serpentine belt, it is reverse rotation as well is the fan blade. Dont mix them....

Which belts did your engine have from the factory?