These are pics of the speaker installation on my 89' 325i. All four speakers are 5 1/4 inch Infinity reference series co-axials. The rear speaker installation was a breeze, all I had to do is remove the stock speakers and covers and then simply bolt in the new speakers and cages. The front speakers on the other hand were a little bit harder. I tried installing them in the stock positions under the kick panel, but the rubber suspension of the speakers rubbed up against the panel. So instead I decided to cut a hole through the kick panel, drill 4 holes for the bolts, and mount on top of it.
I used my Dremel tool to cut the large holes for the speakers and a drill to make the small holes for the bolts. Once the holes were cut and I put the kickpanels back in place and mounted the speakers and cages on top. As I went to mount the hood release back to the drivers side kickpanel I realised that it would not fit with the cage in place. I solved this by putting a few thick washers under where the release should be mounted and using some longer bolts which I picked up at the hardware store. This gave the release enough clearance to fit properly in front of the cages. The results speak for themselves, check out the pics.
Front Driver's side
(yah it's dirty down there I haven't done my spring cleanup yet)
Back Passenger's side
Back Driver's side