in the 70's you could buy 750's with fairings on them, but I think they were dealer installed, an option or not I'm not sure.
I think Vetter produced the hondaline fairings etc which were options or standard equipment on some bikes, but not sure what bikes they came on.
So as far as I know if it's vetter it was aftermarket, if a hondaline it could have been factory/dealer option.
San francisco honda for a while had a 77 750k with a vetter fairing, saddle bags, and a kerker(?) 4 into one on it as a floor display. I think shortly after that they used one of those 6 cylender things with fairing, bags etc.
Ken.