Can anyone identify this plug?

Thanks, that makes a lot of sense. No it's black, (probably from reflection looks a little violet) and it is a 67. I didn't do any of these changeovers. They replaced the 3spd column manual with an auto trans so that's probably why the wire is left over because it wouldn't plug in or they just didn't hook it up like it appears they didn't do with the speedo either. Man I hate having to fix or undo other peoples half-assed modifications. Especially electrical.