41panelmark: Are you using the stock 1940 gauges? If, so you will have to reduce the incoming voltage to them, unless you have already had the gauges professionally converted to operate on 12V. Have you rerouted the wires that used to connect to your firewall 6V Voltage regulator from your original generator?
When I converted my 40 to 12v I used a Constant Voltage Reducer to reduce the 12V coming to the fuel, temp. and oil pressure gauges to 6 V. To make the 1940 BATT gauge read accurately I had to (using knowledge provided by Flat Ernie) isolate the BATT gauge from the other gauges and installed a 60 ohm resister in the 12V wire feeding the BATT gauge. The info. is in thread below. Might be helpful if you're still using your stock 6V gauges.
https://www.fordbarn.com/forum/showt...olt+conversion