I installed 5 1/4" splits in the front.
I had 'em from my previous car, but they were the perfect size, you could probably use 6".
Here's a rough idea of what your up against....
Take the door trim off, don't pry the grill off as it has ONE screw holding it there. ($12 bucks for a new grill!).
- Take old speaker out and trace it's shape onto a piece of MDF (craft wood) at least 16mm thick, mark the holes as well.
- Now use the template supplied with the splits to mark the hole in the centre of the speaker shape.
- Cut out using bandsaw/jigsaw, whatever you have.
The piece of MDF can be screwed behind the inner door skin (using self tapping screws)and the speaker fits into the hole cut in the MDF.
Mounting the tweeters is up to personal preference, but important for staging. My tweeters came with a small pod which can be screwed down and holds the speakers at 45 degrees. I mounted them just in front of the door handle (there is a blank plastic plug) using a small bracket I made up from aluminium.
Clear as mud?