It has been my experience that most 67 cars had the black male/female plug. I have seen the blue two male plugs on 68 cars. Possibly some late 67s used the blue version.
+1 My November 66 actual build date uses the black connector (male/female) version.
Parts vendors list early & late 67 versions and the late version being same as 68.
I imagine the reasoning for the running change was that he dome lamp plug was also male/female (to avoid errors in assembly).
On a side note: Do not tape the two wires of the lamp together the entire length (for any reason such as a repairs).
My original wire had gotten pinched in assembly and a screw cut several strands of the wire. I figured the tape would prevent the wire from breaking. The tape caused too much friction in the movement going back and forth, it would eventually disconnect the linkage rod after about 10 to 20 full swings from Park to Low. (drove me crazy till I bought another lamp harness).