I have an 86 420 SE (euro spec). I am wanting to upgrade the stereo. I looked up the sizes in a store and it called for 4' fronts and 4'x6' rears. The 4s in the front are correct, but when I popped off the rear covers, they were round...no 4x6s. Also, they are raised up in some sort of a pod and angled...so there are no visible screws on the outside. When I measured them from rim to rim it came out right at 6' and the surrounds are very close to the edge...so to me that means they are neither 6.5s or 5.25s. Also, how would I screw them down when there are no screws on top? Can anyone help me here??? Thanks.