[Oldsguy]

Jerry, if the car has already been converted then the starter is probably already a 12v type, You might be able to bring it in and get a replacement that way from identifying marks on it. Another thought, dc motors (starter) are fairly forgiving as far as voltage applied to them. Your starter would just spin faster with 12 volts applied compared to 6 volts if it is originally a 6 volt type. Perhaps after long years of use if may fail earlier or if it was running for a long time it might get hotter but starters only run for a few seconds at at time. Another thought, you might be able to take your problem to a shop that rebuilds starters/motors/alternators. I had an alternator rebuilt for about the same price as buying one from the local automotive chain store. Having local support and knowing a local skilled tradesman did it made me feel better about the whole thing as well.