Doug,
The oil cooler does not need to be functional. The way it's designed, air will exit through it open and closed. Notice that when the real one is closed, there is still an opening. It is strictly for scale purposes on a model. As far as the temp sensor unit, I think it is really a neat item. But not needed on the P-51. Revert to the KISS theory. But if you want to make them functional. Use the throttle as the master and the servo for the oil cooler as the slave. This will be the easiest way. I have attached another picture to show where my firewall is opened up. This is all you need. The hole by the carb is about 1 1/2 inch diameter. The switches don't impede cooling.

Karl