Hi, I am getting a new carb for my 1976 Motobecane Cady. Right now the existing carb is a Gurtner Brevete, with a 215 jet size. The Cady's motor is either the m1 or m3 model. Im not sure which size dellorto I should get. Whats barrel size, choke size? Help from a seasoned carburetor expert would be greatly appreicatied