6V is 139 teeth and 12 volt is 168 teeth. If you are coverting to 12 volts you can use your 6 volt starter, or you can convert your six volt to 12 volts, any electrical shop can do it.
Or you can take your flywheel to a machine shop and they can swap out the ring gears. I had my flywheel ground and ring gear changed for 70.00 dollars.

1942 G5106 1.5-ton Chevy cargo dump Gallery page




Old Dominion Stovebolt Society
T/Sgt. Gott (28 years of service with the USPP)
1940 Chevy G506 4112 cargo dump
1942 Diamond T G509 969A 4 ton wrecker
1942 Ward LaFrance G116 series 2 10 ton wrecker
1944 Ward LaFrance G116 series 5 10 ton wrecker
1931 Ford AA with a WEAVER crane
1944 Sterling HC 165 tractor
1944 Autocar U7144T w/ 10 ton trailer