The 261 engine will run on either 6 or 12 volts equally well, so just go with whatever system you have at the present. If you choose to keep the original 6 volt system in place, simply use the flywheel, clutch, and starter from the 216 on the 261. There is a difference in the number of flywheel ring gear teeth and the tooth pitch of the starter pinion on a 12 volt setup, so the starter and flywheel must match. The 6 volt flywheel has 139 ring gear teeth, I believe, and a 12V flywheel has 168. Mixing and matching starters and flywheels results in noisy operation and rapid gear wear. The distributor doesn't care what voltage is used- - - -it's the coil that needs to match up, voltage-wise, and a 12 volt ignition system needs a resistor wired in series with the coil to prevent burning points. No resistor is needed for a 6V ignition system.
Jerry
