Several things that you may want to consider before performing this conversion.

This would seem to be a pretty straight forward and quick job, however, in addition to the starter; you’ll want to at least consider the ignition, lights, starter, instruments, windshield wipers and charging system.

If this is an occasional driver, the original ignition system may run fine with just the addition of a ballast resistor for the coil. If you’re going to drive this one more “than just around the block once a month,” a new 12 volt coil probably makes good sense.

If your current 6 volt is a standard coil found on most domestic vehicles you will need a ballast resistor. I believe most 6 volt coils are rated for 8 volts. Some aftermarket performance coils may work without a ballast resistor, and you could try your current coil – bearing in mind that 12 volts may ruin it. Using a true 12 volt coil will eliminate the need for a ballast resistor. Your original points will work fine in a 12 volt operation. The AC Delco U515 is a “universal 12 volt coil that does not require the use of a ballast resistor

Your condenser can be replaced by any condenser, i.e., AC Delco A202Z is a pretty universal condenser with an open lug and a side mounting bracket

If you don’t replace lights, the bulbs will begin popping like the 4th of July. You’ll need to change all of them – tail/brake, headlights, instruments, dome, license plate and trunk/under hood if you have them. The easiest way to do this is make a chart of each place a bulb goes, remove the 6 volt bulbs and head off to the local parts store to make sure the ones you select will fit. Most will be standard bayonet bases. Bear in mind, some may be a bit different in actual light produced. The headlights are the easiest as you’ll replace with a new sealed beam (go halogen) unit.-

The starter is easy - it will work well on 12 volts. The 6 volt starter is designed to handle a significantly more current a 12 volt starter. The solenoid needs to be replaced with a 12 volt unit as it will overheat with any lengthy cranking and could possibly stick in the ”on” position causing your starter to overheat and that’s bad. I hope is goes without saying that all cables need to be in good shape and very clean. If in doubt, replace them with nice new heavy ones.

The instruments are tricky. If you have the stockers and want to retain them, you can use a voltage reducer from AC Delco. The AC Delco U1745 has a 4 amp load limit. You will need one per gauge to do this right.

Good ol’ JC Whitney has a “12-Volt TO 6-Volt Wiper Motor Voltage Reducer – Part Number ZX737160X $38.95. It’s specifically designed for a 6 volt windshield wiper in a 12 volt system

The easiest and most common alternator unit is the GM 10SI or 12SI units. They have the internal regulator, and require only 3 external connections. They also gives you the option of using a 1 wire regulator (self-exciting regulator) which requires only 1 external wire. You may have to coble up some brackets or use some from a donor vehicle. Really all you need is a pivot bracket and a top brace to keep the belt tight and in line.

Hope this helps (and doesn't discourage). Oh yeah, one more thing - you can not have enough good ground. Clean and heavy gauge straps are your friend here!

Regards and Have Fun,
Glenn