I assume that you are using the 62 motor but the flywheel and transmission adapter plate are still from your 54? It is enclosed driveshaft right? Don't get bogged down in the 6V 12V stuff. you will still use the 6V starter as that is what will match up to the flywheel. If the truck is converted to 12V, You can do what I did. On the advice that a 6V solenoid running on 12V would be a little "harsh" hitting the flywheel teeth, I found a 12V solenoid that fit. The starter motor itself will be fine on 12V and last easily as long as you don't grind it for extended periods.
