[Rick Parker]

The nipples or ports on the top at the 10:00 O'clock position, depending on the casting or brand of pump being used are all on the "Low" (read unpressurized) side of the pump. This means regardless of whether you are using a serpentine or V belt pump water is drawn from the bottom of the radiator, forced into the the large openings in the block, (now presurized) in and around the cylinder bores, through the openings in the top of the block deck surface, (some manifolds also have a rear crossover to equalize pressure), then into the heads, then flowing to the front crossover and out through the thermostat housing, heater hose and or bypass hose and into the water pump ports and top radiator hose.
The serpentine belt arrangement and resulting reverse waterpump direction was necessary when designing the overall accesory drive packaging and to provide for enough contact with the back of the serpentine belt to drive the pump, AC compressor, power steeing pump etc. I think it also has the side benefit of less parasitic loss.