The C-codes in pre Fox 4.1 Granadas, Monarchs, Versaillies from 1980 to 1981 had 'em. Worth 4 hp at 4800 rpm on a 98 hp net engine, 102 with it disengauged. The SAE net and DIN net readings are generally with the fan fully engaged.
So did 1980 onwards Alloy head 3.3 and 4.1 Falcons, a factory part as a viscous fan (wax filled).
They are compact enough, and not too much trouble to fit and remove if you have the right FoMoCo visous fan puller, but they then started playing with the fan pitch to reduce noise, and the early fans often won't accept the later viscous fan clutch unless you install them both.
Best wind rush is by the stock early fan (1969 to about 1980 Australian, US C9 to about 1975 [D5?]). Any time noise is reduced, air flow at idle is reduced, so just a thermostatic fan clutch is a huge advance.