Originally it used mech. linkage. I would recommend using a hyd (as they are the best), then a cable, and lastly mech. Hyd cost a lot to do, but it works the best. Cable clutchs are nice and smooth, and mech....well, I just don't like them. There is clearence problems with headers, they can go out on pretty easily (with my experence at least) and they are not a nice smooth operation. Double check this, but your motor should have a thread hole on the driverside of the block for a piviot shaft to screw into for a mech linkage set up.
-Shaun