I could take a picture of the installed valve if you want but it wont be too exciting; just an inline valve with the push-pull cable attached...
I wonder about the ball valve idea you guys are discussing. You would have to get out of the truck (probably in pouring rain) and open the hood when you want heat? Then it would get too hot and out you goo again. I know you could open the window to regulate the heat, but then you would have the rain blowing in...
