The Dynon 800 & 1000 displays supports a fuel system where fuel run back into a talk using two red-cubes. If the 180 doesn't support a differential fuel measurements (I am not familiar) then you are out of luck the red-cubes just output a digital signal where the number of reported pulses is an indication for the fuel flow. You would have to measure the number of pulses in red-bus in a period of time and subtract the number pulses that the return flow red-cube reports (assuming both have exactly the same calibration factor), this can't be achieved by just connecting the outputs of the two red-cubes (unless you add more complex electronics that can calculate such a difference).