start with CR750.
To tell the truth, Honda kinda pulled out of factory involvement following Daytona in 1972. Anybody running honda's after that were largely privateers. The next time Honda stepped up in racing was when the DOHC bikes came out and the new venue was endurance racing (specifically the Bol D'Or).
Look up, the CR750 as a starting point. Then look for Seely, Magni, Japauto, rickman, any of the other "specials" builders since they all made bikes using even the 77-78 K bikes as a starting point (my rickman frame is a 1977). cruse around on satanicmechanic.de for a while - he has a lot of pics there.
are you starting with a K bike or an F bike? Carpy has build at least two F bikes with CR style tank/seat combos so the vintage race setup is certainly possible - plus the rear disc gives an added race look.