Hitch Descent Rate Valve

My early D14 lacks the valve that adjusts the hitch descent speed, and since the wife will be driving it for the first time this spring with a mechanical transplanter and me in the back, I'd like to plumb something in the hydraulic line that accomplishes the same result and prevents the wife from dropping me and the transplanter hard. Are these just needle valves/flow control valves? Would it really matter where I'm the line I plumb it in (in thinking at the rest end instead of under the gas tank)? Anyone have a good picture of a factory valve? Thanks in advance!

There is not a "rate-of-drop" valve for a D-14 tractor from Allis-Chalmers. There is such a thing as a "one-way hydraulic flow control valve" that has a speed/flow control knob on it for less than $30 bucks. Use Google to find one. Place it at the rear to the left of the seat  between the steel tube elbow and remote coupler manifold. One way it restricts flow and the other way is free flow.