Greatlooking Alan! You have the Competizione model, as opposed to the super record with the "aero" seatcluster and engraved lugs, probably an early one. Look for a 25 mm seatpost (alan or vitus). As for dating the bike, SN number on mine is A79476 and it's a 1976 model. Later Alans had simpler numbers on th seat tube (eg 783, july 1983). I have an emailadress for Alan where they're very helpful answering questions like these. If you want to contact them, I'll send you a PM. Oh, and it doesn't need an ava stem!