The above method is by far the easiest. however, if you are running real deep 6x9's and have the torsion springs that cross under your speaker openings that can cause clearance issues. However, if I remember right, by 85 they were hydraulic.
I have also done an install where I used MDF and mounted them down below the openings where the flange is (this was on an 81 cutlass). I used 2 pair of 6" round speakers and then suspend-mounted the tweeter in the original opening. From inside, it looked totally stock. If you are interested in this method, I'll elaborate, but the car got totalled out 10+ years ago so I am a little hazey on the details.
I have also done an install where I used MDF and mounted them down below the openings where the flange is (this was on an 81 cutlass). I used 2 pair of 6" round speakers and then suspend-mounted the tweeter in the original opening. From inside, it looked totally stock. If you are interested in this method, I'll elaborate, but the car got totalled out 10+ years ago so I am a little hazey on the details.
