Hmmm........ Is that 7414 number referencing the engine number or the frame number ? Looks like 7414 probably is the engine number, NOT the frame. On a little closer study on my behalf, i note there are no chassis parts given reference to 7414.
I just assumed Honda would reference changes by frame number, not engine number, since vehicles are registered by frame number, not engine number. Have never really givne the 7414 number much thought or study.
Another interesting note - page 127 of my February 1971 parts manual, notes different p.n.'s for frame CB750 1000001 to CB750 1003950. Is CB750 1003951, when the horn mount was switched to the RH side ?