Mate from me being an Auto Electrician I find it pretty easy to say get a new one!
( Just because if it is somehting electriacal we either have it in stock or can get it for a good price anyway!)
But I have noticed that the other guys around here don't feel the same as this!
Like I have said before you can get stuff from a wreckers as chances are the car didn't go there because the part you wanted broke!
But being it an electric fuel pump you want
I have found from experiance that at wreckers they have usually been run dry when the wreckers have drained the tanks or that because the pumps have dried out that they have bits of dry stuff in them and they maybe work for a few weeks but eventually this crud breaks loose and siezes the pump!

Don't know of any cars offhand that have electric fuel pumps as most like Swifts and Geminis have theirs inside the tank and these would be very fiddly to fit to a tank!

( I do know that Holley do have low pressure hi flow electric fuel pumps! but if you got this you would be getting brand new!)

**** Another thing you could do if it is just for the immobiliser is get a fuel cutoff solenoid! ( It is basically like a tape it shuts off the fuel when power is removed from the solenoid! *****

Or you could just use the fuel pump cuttoff wires for another ignition cut out!
( I would look towards the fuel but as a datsun is pretty easy to start even if it does have an ignition cutout!