Point of information.
The last mark of 172 to be have the 40 flap setting was the 172M. Subsequent marks only have 30 degrees. The later models also have the "lever-in-a-slot" rather than the switch and gauge for lowering the flaps.
(at least this is true of the M, N, P, R and S models of 172 that I've flown)
However the 182 still retains the 40 degrees setting.
Brooklands