If you are referring to a 2004 mustang
, your door speakers are 6x8's. A 5x7 will also fit this hole. If my computer was up and running, I have detailed instructions with pics on there. Basically, what you want to do is look at your door. The part with the window switches that is a different color, that pops out. It takes a little pursuasion. You pop this out, there are 2 phillips head screws holding the switches to this panel, take those out and set the panel aside. Now, look in the spot where the panel was. You will see either 1 or 2 black head screws in there kinda hidden. Take those out, they are phillips head as well. Next, look on the part of the door closest to the hinge. There is a plastic "christmas tree" right there. Take a flathead screwdriver and pop it out, being careful to not damage your door panel. Now, once the 2 screws and the front "christmas tree" is out, pull upwards on your door panel, it should pop right off. Now, your speaker is held on with 4 phillips head screws, take those out, unhook the speaker and either tap into your existing speaker wires or cut those and put connectors to connect to your new speakers, reverse the steps and you're done.