[rotorwrench]

Most 12-volt conversions either have a later type 12-volt generator or they have an alternator conversion. The larger 12-volt generator will work better with the later 8BA engines due to the larger generator mount. If it still has an original generator then it is most likely a 6-volt set up. The alternator converted generator bodies like the power gen, still look different than an OEM unit. Some are actually converted using the original generator case but you don't see that as often.

Another check would be to look at the light bulbs. They will be 12-volt types if converted and generally still have their numbers printed on.