I did a search and see a ton of references to people doing this with good results, but where do you actually mount it, and how do you get access? Also, which side is better, and where's the best place in relation to the cowl to run wire through the firewall?

 

Mine is just an 02, but have it mounted on the passenger side, cowl was not difficult to remove at all.

 

I did a traditional install on the roof, with the antenna right in front of the brake light. It was actually quite easy.

I took a metal coat hanger and made a fairly small loop to fit the antenna "plug" into. Pulled the weatherstripped away from the passenger side door, which allowed me to push the coat hanger towards the brake light. Once I got it lined up right, was easy to pull the wiring through.

The reception on the roof of my truck is considerably better than the reception on the roof of my old Focus hatchback.

 

Today, I mounted a Sirius antenna for a customer. I placed it where the defrost vents were, to get access to the spot you remove the bezel around the radio, drop the radio down, and where the defrost vents meet the top of the dash behind the radio, you push the dash up and slide the antenna in place. It does not affect signal to my knowledge, when i tested it it worked perfect, no drop out at all.

Here are some Pics.