I have a top draw with a 1" cheap water pump.  There is a 90 degree hosebarb at the top of the tank with a good suction rated fuel hose down to the pump.  I put a ball valve just before the pump and always turn it off while the pump is not running.  Never had an issue with it losing prime that way.

My thoughts are that a 1" pump might fill slower but will also not create as much foam in the tractor/combine tank and not cause issues with the auto shut off nozzle.