Tomos motors make a good swap for an old moped. Pedal start A35's being my favorite. 50cc reed valve, 2 speed transmission, quick stock with plenty of performance potential. Replacement and tuning parts are available. The A55's are nice too but have a bit of extra stuff like electric start, so you'll have to do a little more wiring. Sachs with tomos swap.
Swinger2durring tomos swap.