I realize this is an old post but I was able to convert the mechanical voltage limier inside the fuel gauge to an external electronic style. I also swapped the gauge behind the face from my square/rectangular style with a round 65 style. Works great. Now the fuel and temp work. Ammeter was bypassed. Both wired to a single stud.
Just as a side this is the only mopar I have ever had that puts out 14.2 at idle!!!
