Quote Originally Posted by agr071 View Post
IMHO the underdash is the most efficient, then factory intergrated, then the one you cut the glovebox for.
I agree that the under dash is the most efficient, that's because the fan is blowing straight over the evaporator into the cab and doesn't have to go through ducts. If you are installing a factory one you can insulate the ducts to make it more efficient but you still have the undersized evaporator next to, above, the exhaust. In saying that though i would still prefer to put in a factory system, just don't like the look of the under dash clingons