I built my own OD control circuit. I can "split" the gears and get six speeds. For the kick-down switch I used a spring loaded toggle that only makes contact when the toggle is engaged (up or down). As soon as you let go it returns to a normal open position. The momentary closed position mimics the stock distributor kick-down switch action. As someone mentioned you can also mimic this with "kicking" the gas and letting off quickly. FYI: what I did was read the manual regarding the operation of the circuitry and design my own circuit because I didn't think the one that I saw on-line ("Burbs" website), would fit what I wanted. I used three Bosch relays, two switches (one for kick-down and one for power) and two indicator lights that display normal mode and momentary kick-down mode. Not difficult, just takes a little time.
