I asked this question deep in another thread, but it got no play becuase of it I think so I thought I would ask it on it's own. if you ran both + leads from the sending units on 2 different tanks (your main and the auxillary) to a 2 position knob and then from said knob on to the + post on the after market gas gauge on my dash that is currently setup to read only the main tank, could you not then turn the knob and switch between readings from 2 tanks? NOTE: both tanks would use the same brand/style sending unit made to work with the same style/brand gague on my dash so perfect compatability. can anyone with good wiring knowledge confirm if it is infact as simple as I think it is logically and just adding a turn knob inbetween the gauge and both sending units to make it possible to flip flop between 2 tanks on 1 gauge? if it is possible.. I believe I need a SPDT (single pull double throw) switch that has 3 posts (1 for each tank and 1 to gauge) and is always on (on-on) and has no off option. that is, the switch is either A or B and no dead center. correct?