I have never installed one, but I have to replace one in my truck, and it is best to do it when you are already dropping the coolant, because you are going to loose all of it when you install a heater. These trucks had them as options when they where made, I think. I will see if I can post a photo later of the one in my truck.

 

Thanks, another item for the coolant flush project.

A photo would be nice, when you have a chance

 

I replaced the thermostat with an OEM Delco stat and it seems to be heating much better. I still plan to flush coolant this spring.

Also, I found it has a block heater! The cord plug was tucked into the underhood tool box. It works well, too!

 

Now thats nice! Usually those are burnt out I think!