You can put a 6 Volt flywheel on a 12 Volt engine. The crankshaft is the same diameter at the journal. It is drilled and pined the same. The flywheel was probably used because it fit in the Bell housing. And the bell housing fits the cross member. A 6 Volt stomp starter will work just fine in a 12 Volt truck. As long as it is not run for long periods and over heated. Some one will know, but I think the Armature shaft is bigger in a 6 Volt Starter motor. The mismatch from the mating of gears that don't mesh is what causes the noise. The "Bendix" drive is different for the 6 Volt because the shaft diameter is different. Find a 6 Volt starter and try it. If the flywheel is not too damaged it just might work. And if it won't then you can pull the flywheel off and get a new ring put on it. The starter is 2 bolts and a cable, The flywheel...wel that is a bit more work..He,He.

Steve H