Gauge voltage and Fuel relay with AA classic install

A relay location does not need to be close to the load, so long as the wire from the battery and to the load is large enough to supply it. If the battery is in front, and the pump in rear, it makes no difference which end of the car it is located

If both pump and battery are in the rear, it would make sense to relocate the relay. You don't need to add one, you can abandon the one there, and install it or a different one in the rear, then just extend the trigger wire from the supplied one

If both the pump and battery are in the rear, it makes sense to move the relay, because now you have to have adequate power wire all the way from the battery (or the battery main wire) from the trunk, and then run it right back all the way to the trunk