8/74 and later.
From MAF.
Centerforce Clutch Assembly for 6-Cylinder Applications
"For those of you with an 8/74 and later Land Cruiser running the OEM 6 cylinder with the diaphragm clutch assembly, we are proud to offer what we feel is the best clutch available for your vehicle, the Centerforce Clutch assembly. The unique design of this pressure plate gives stock pedal feel yet 30% greater than stock clamping power. This is accomplished by putting a series of weights connected by a retaining ring around the center of the diaphragm fingers. As the engine speed increases, the weights are forced apart by centrifical force, lifting the fingers thus creating more clamping pressure. This pressure plate combined with a new Centerforce Clutch Disc gives a clutch stock feel and pedal pressure, but substantially more clamping power than stock to prevent slipping and insure long life. ..."
"can be used on early Land Cruisers that convert to diaphragm style flywheel, t/o bearing, and fork."