I am installing a GSC Race Shaft in my block, and I remember reading somewhere that the oil pump sprocket can be rotated the wrong way. How can I make sure the gear and shaft are lined up correctly?

Install it
The alignment is for getting balance shaft timing right, since your replacing it with a straight shaft timing the sprocket isn't paramount.
How ever if you're reusing a oil pump you really should have the gears run to their original mating counter part sprocket.
So there's a dot on the balance gear that should face you when installing into the oil pump housing and it should line up to outside of the oil pump