Dual Field Alternator Conversion - New Electrical Gremlins!

No, there's something else. You have some harness wires crossed or melted

The IVR receives it's power from the ignition switch----same power operates oil and brake warning lamps. The IVR output only goes to the temp and fuel gaues (unless Ralley) through the gauges, and then out the sender wires to the temp sender and to the fuel tank.

That may be very bad. You may have "other things" burned up including part of the cluster PC board and or gauges.