Producing 66.6 hz signal

Hello guys, I am trying to build a device to troubleshoot aftermarket cruise kits that we install into vehicles. Sometimes we have a cruise that will not work and a poor/no vehicle speed signal is the likely culprit. WHat I need is a device that simulate a 60 mph signal to my cruise module. Typically we would want a square wave signal that will go low 66.6 times a second to simulate the 60 mph speed. I found this ;

The only problem is that it produces a 1khz signal. Can anyone tell me what components I can swap out to achieve the desired 66.6 hz signal? If you go to the "download" section of the Mk105 it shows the schematic. Help please......