[redmodelt]

It was stated that it's running rich and only getting 10MPG.
What condition is the motor in?
Have you checked for vacuum leaks?
Are you using the GVA and setting the spark correctly?
Has the timing been checked?
If the GVA is open too far to compensate for a vacuum leak then you could be running too rich which would carbon up the plugs and the motor would be flooding. I find it hard to think that having tried that many carbs that there aren't other problems.