This is a RC 4-1 for K7. My bike is a 1977 according to the registration, K6-1976 is the real build date.
I ordered the 4-1 to a 1977 and got wrong.
I removed the spigots on the head, bought 1977 versions with bolts. The rear mount was also wrong, had to add 4" extensions for the passenger foot pegs. The tilted angle looked tough though.