The AC Delco parts listings had the original pump listed with a photo that was a direct match. Couldn't find a Delco pump available but the Delco book cross referenced the Fuelmiser pump number which was available, so I ordered the fuelmiser pump.
Didn't even bother enquiring about genuine Nissan parts- pricing is normally calculated on an additional 300% sucker surcharge.
Didn't expect the O ring to leak for the reasons you mentioned, but all hoses are secure and the fuel leak is coming from the O ring area - Impossible to see with the tank in place in the car.