72 360 first start question

Priorly you set the slit at 15BTDC and lined up the magnet with the tooth. Was it still in that setting when you swapped carbs? If not then I would set it back to that & holler what happens. If yes then we might put a light on it now & see if we can get a reading (a dialback would be handy here). What is the lowest RPM you can get it to idle at now?