The 6 volt 6 bolt flywheel is found in 1954 and both series of 1955 GMC pickups with a 248. Sometimes its easier to find a whole parts pickup than just a flywheel. They used the same casting number for 6 and 12 volt flywheels. On one or the other, they machined the casting down a little more so that the 2 ring gears are not interchangeable. And as John says, the only way to tell the difference is to count the teeth
