The voltage reducer should have come with instructions on which end of the gauge to install it.

I've never seen a '46 instrument panel. On the '48 to '53 panel the terminal nearest the "E" on the gauge is connected to 6 volts and the terminal nearest the "F" is connected to the sending unit.

'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.