[Mr70]

Part #3931002 is for the entire Fan Assy.
The other #'s I believe are the individual blade #'s.
The Clutch Viscus they used varied on the vehicle it was applied to.

That's a Sept.1967 date code that came on:
*1968 Full size 396 & 427(Not Solid Lifter)Passenger cars w/AC.-used Clutch Assy.#3931004
*1968 307 Nova w/AC.-used Clutch Assy.#3916139.
*1968 Small block Camaro & Chevelle w/AC-used Clutch Assy.#3916139 also.
*1968 Chevelle w/L-79 327 engine.-used Clutch Assy.#3916139 also.