I had a response recently on an older post, as there are none in the rear doors on mine there /should/ be wiring but nothing riveted/screwed in. The 6.5inch slim line ones are it seems what you want to use.
Hi guys, looking to fit speakers in the rear doors of my 55 Focus Ghia. the holes are already in the door card and I was wanting to know how easy it is to fit speakers. Also, what speakers would you suggest and finally, will it work with the standard head unit fitted (non Sony)