I put a 91 Mustang 302 HO in my 41 Merc However, I want to keep the factory gauges. What do I have to do to make this possible.
You have to use the sensors that were on the engine in the '41 Merc, and adapt them to the 302. Then install a voltage reducer/regulator under the dash for the power to the dash gauges to bring it down to 6 volts. (assuming the car has been converted to 12V).