Audio Systems: System, ford mustang, factory stereo

Question
I'm interested in the PA systems at http://www.seeoursound.com/rei/mobile.htm - more specifically, I'd like one of the $325+ AM/FM/CD/PA systems. I am confused, though, about how they are installed and how they fit. I will be putting it in a 1998 Ford Mustang - I tried to measure the space where my factory stereo is, but I have no clue how to measure that because I can't get the ruler to be even with it. Do you know what the size of the factory stereo on a 1998 Stang is? Also, how do these panels work? If I want one of these systems but it's too big to fit in my car, am I out of luck? What if the panel size is too small? Can it be made bigger?

Thank you in advance for your help.

Answer
Hello Steven,
Please give me some details about what you are trying to do with a PA system in your car. Also if you would like to save over $100 on this type of set up please contact me direct for details.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net