???

What I do on all my installs is actually take the antenna and mount it behind the a pillar. Obviously if you have air bags you will need to mount it behind the air bag in case it was ever deployed. You will get full reception and you wont see it, making a very clean install.

If you dont want to do that, and your antenna is small enough. You can carefully place it under the sunroof flap. The one that moves up and down when you open the sunroof. I did that on a satellite radio install for a customer a while ago.

external?

i think he was talking about portable gps like tomtom or garmin, the ones you stick on the windshield?

in which case i would say.......windshield?

then in that case... yes windshield lol. Check your local laws first before sticking things on your windshield, it may be illegal.