I don't know if you will consider this help but my recommendation would be to leave it 6 volt .

What are your wanting to achieve by converting it? If it starts and runs OK now are you wanting to run modern accessories? If so you can buy 6-12 volt step-ups to power the accessories for a lot less than doing a conversion. If you're wanting to make it look stock you'll not be able to do that with an electronic ignition (at least I'm not aware of one that uses an electrolock coil). Doing the conversion is fairly simple. Doing it and making it look stock is more difficult. As for the harness, if you're wanting cloth covered wires you can buy pre-made harnesses from YNZ Yesterday's Parts or Rhode Island Wire. A 6v harness will handle anything 12v can throw at it but a 12v harness cannot handle 6v current requirements.

The car is not running as I am restoring it.  I have been told that a 12 volt system is more reliable to start and the lights are much brighter.  So these were the consideration for converting

I have a 39 Master Deluxe I have been driving for the last 53 years. The 6 volt system and point ignition have never let me down. It is your car to do what you want but consider the benefits of keeping it stock and the factory manuals can still give you the step by step help.

Dave 

Posted by: @david-black

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The car is not running as I am restoring it.  I have been told that a 12 volt system is more reliable to start and the lights are much brighter.  So these were the consideration for converting

If you convert it and keep the 6v starter it will normally start easier because the starter will turn faster on 12v. A healthy 6v starter with clean connections won't turn as fast but will start a healthy car with no issues. My 38 is still 6v but I put a 6v alternator on it in place of the generator. The upside to that is it charges even at idle. The down side is it ruined my ammeter. There are normally brighter lighting options for most 6v applications. For your headlights, if you still have the stock reflector that uses prefocus base bulbs you can use 2530 bulbs instead of the stock 2320 bulbs. I use them on my 38 and have plenty of light even with my reflectors needing re-silvered. The tail lights on a 39 can be an issue. If you have the single 1154 bulb, there are halogen bulbs available for 6v applications that are much brighter. I can't be too critical of converting because, while I kept my 38 6v, I converted my 53 to 12v. If you do convert just keep in mind everything electrical (except the starter and horns) will have to be changed to 12v (if available) or have resistors put in-line to reduce them back to 6v. The starter and horns will normally work fine on 12v as long as you don't over use them. The horns will be very loud.