After re-wiring my fuel pump wires and new battery and better wires all round etc etc.
I only see 13.5/13.8 volts at the fuel pump and it is\as I have been told because of the length of the wire from the battery to the pump.
But as said above 12v or slightly above is perfectly fine to me.
I think the fact that the alternator to battery wire is so long is were your losing some voltage IMO. But then I am not a mechanic lol.

Hope you get it solved