As cletis posted, you can't use a 12 volt starter with a stock '54 flywheel.
Additionally, you do not need to use a 12 volt starter when converting to a 12 volt battery.
The 6 volt starter not only works powered by 12 volts, it starts the engine Right Now since it turns the engine faster.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission