In the rear, we run Moped hubs for our Morini powered bikes, my personal preference is the Puch hub. It's a 130mm width, so if you start with a coaster brake frame (typically a 110mm width) you need to widen the drops. Also, because the hubs have 12mm axles, you need to open up the slots to get the axles to fit. The front axles are 11mm.
These hubs have bolt on sprockets and the offset is a perfect match to the Morini motors, and the offset works on the bicycle side as well, so the chains line right up. The hubs are also pre-drilled for big spokes and the std sprocket size is a 45 tooth which is good for all around riding. Good stuff.
Up front, most guys still run the worksman drum hubs, but I'm running the matching Puch hub on the blue bike, the axles are larger and they have better backing plates that are located via a pin rather than a strap around your pretty paint job. Otherwise, the hubs are almost identical to the worksman hubs -I'm guessing they're made by the same manufacturer. The pads are even interchangeable.
Rich