When I changed from a 7-blade CCW rotation fan back to the OE 5-blade CCW rotation fan, I also replaced the thremo-fan clutch just because the OE clutch had 160,000 miles on it. Even with that many miles, the OE thermo fan clutch seemed to still be in good condition.
I installed a new AC Delco 15-4630 (GM-15709933), CCW rotation, thermo-controlled fan clutch. I purchased it from a seller on e-bay, NIB, for $60. It is still available from GM for $182 msrp.
LOL I did not know they still made those green fiberglass flex fans. A 1969 - 1970 Pontiac GTO with the Ram Air IV engine was equipped with a steel solid flex fan.