There are spacers,FT175/1 x 2 a stud F35/1, washers and two 3/8" B.S.F. nuts. needed to fit the horn properly. The "LUCAS" on the chrome bezel is uppermost, but it is probably better to fit the terminals at the bottom, keeping live leckertricity that little bit further from fuel and places it might cause sparkles. This is different to the standard Twin fitment. You probably know all this but the horn should be HF1234 with a raised bezel, hexagon acorn nuts and a flat alloy tone disc. I believe some 1951 machines had alloy or MAZAK bezels, can anyone confirm this?