My water pump is starting to make a sound - figure it is time to replace it. I have an F motor 74 fj40. I know that there are two water pumps different by one inch. SOR indicates that I need the smaller of the two. Does that sound right? I am ordering a gasket. Besides that - while I am in tehre should I do anything else? Also- OEM is about $50 extra. Is it worth the $50 or is aftermarket OK?