Dennis Carpenter Voltage Reducer

[Ramblin Reck]

I am looking in MAC's Catalog at a Dennis Carpenter Voltage Reducer-Reduces 12 volt to 6 volt-Dash Gauges for $35.00 (SKU 66-62256-1) The only problem I see and it may not be a problem, is that it shows three gauges: FUEL, OIL and TEMP. My third gauge is a volt meter gauge for the battery. The TEMP Gauge is a mercury thermometer gauge on my 1939 Ford Deluxe Convertible. Will this device still work and what will my Batt gauge which is the third gauge in my cluster show? Thanks for y'alls help.