[tommyleea]

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Originally Posted by 55blacktie

Following Gil Baumgartner's (CTCI, Gil's Garage), I converted my 1955 Thunderbird from 6v to 12v. There was no need to replace gauges or sending units, or use a voltage reducer(other than for the radio, which doesn't work). Don't mix 6v gauges with 12v sending units and vice versa. You will have to replace all 6v bulbs with 12v. If you have other questions, I suggest you read Gil's article.

Thanks..I will take a look at the article

Originally Posted by dmsfrr

tommyleea,
Here's a link to the article....
Doing the 6v positive / 12v negative ground conversion isn't as complicated as you're thinking...
https://www.ctci.org/battery-for-6v-to-12v-conversion/

The '55 Fuel and Temp gauges work on current flow and heat, controlled by bi-metal switching contacts in the senders. They should not be voltage or polarity sensitive, but do need to be a year matched pair in good working condition.

A ballast resistor will need to be added in the existing power wire to the ignition coil, as well as another wire from the new 12v starter solenoid. The ignition coil is polarity sensitive so its leads should be reversed. Diagram below...
If your truck has the battery cable to the starter solenoid on the large left side terminal (not on the right side as shown in the diagram) that's normal, it makes no difference.
If you use a 12v generator you will need to polarize it before starting the truck. The procedure is in the article.

I'm betting getting the 6v generator rebuilt is less expensive than all the new 12v parts you'll need.
If it's just the positive / negative ground thing that's annoying you, you can switch that just by changing the battery cable connections, switching the wires on the ign coil and re-polarizing the generator. On the chance the truck has a functioning 6v radio it may not be polarity sensitive, like the dash clocks are.
If the 6v setup is working well for you there may not be a pressing need to go to 12 volts, unless you're wanting to add 12v accessories to the truck.
One of the bigger shortcomings of some 6v vehicles is having the incorrect size starter and battery cables. They should be zero or 1 guage cables, not anything smaller or they can cause sluggish starting.
.

Thanks for the info..So it appears I don't need a voltage reducer for the dash gauges, unless they don't work, then add the reducer.

Do I have to run a wire to the I terminal of the starter solenoid? I would like to keep using my push button to start? My ignition switch doesn't have a start position.