This list was garnered from the MPC regarding shrouds, fans, spacers and clutches:
Boss 302 and 302,351W with a/c or x/c C9OZ-8146-A fan shroud marked C9OE-F for 24" radiator
Boss 302 and 302,351W with a/c C8SZ-8600-B fixed 5 blade fan marked C8SE-B (351W x/c fan same as std)
Boss 302 and 302,351W C8ZZ-8546-B fan spacer marked C8ZE-D
69 351W C9WE-C 7 blade clutch fan
69 351W C9WE-A fan clutch
The same two fans Jeff spoke of are in the list.
I have one C8SE-B (stamped on the steel frame) with aluminum blades
C9WE-C (stamped on the aluminum blades) is common on Cougar.
It's correct for 351W, but I'm not sure if it's for Mustang?
I have two of them, one with clutch and one without.