your electrician is wrong. There was no diesel charade with this gauge cluster, If you want another proof - the rpm meter in the diesel charade redlines at 5000 rpm.
For this type of gauges the tachometer was driven from an external amplifier box that was mounted to the firewall of the car.
Find a gauge technician, they will be able to drive the tach, its not very hard for them to do.
I dont quite recall the exact name of this model of G11 that came with this gauge, but it had the strangest interior color - very dark blue with red printed squares (not checker design) on the door cards and seats. It also had brushes alumnium finish on the A/C control levers and door pulls.