I have used this VSC in a few different applications. It is a soft start variable speed controller so it is easier on the fan and the charging system. It uses a probe in the rad fins which is placed near the hot water inlet area.
It has an adjustable set point 155 -240 deg and ramps the fan from 60%-100% speed according to the offset between the set point and the actual core temperature. It has a limit of 45 amp load so it may not power both fans, you would need to take an amp draw of two fans running. It will require a signal form the ignition to tell it to shut down after a 30 second delay. It can also accept a signal from a 12v source to force on (100% output) the fans to give a manual over ride. You could wire one fan to it set at 175 and have the other fan activated via your current controller set for 200. If you are running two fans on separate controls have the fan that is closest to the rad outlet start first and shut off last.