An on-off valve is handy when water is in short supply. You can use the heat exchanger to heat a bucket of water and using the valve take a shower using minimun water. The following gears will be needed. The numbers should be stamped or cast on each gear. The transmission used will determine the input gear.
Some cases require a little grinding for clearance of the larger gears.
Power take off won't work with out special gears. When I added a front hoop for a roll cage on my CJ7 the window crank would not clear. I bought a pair of ratcheting offset box-end wrenches. The offset type will ratchet in either direction with the push of a botton. Cut the center out of the old cranks and grind a hex shape to fit the wrench.