I decided to jsut install a new system in my 1992 960 but I have a few questions I need answered. First how do I drill out the speakers, I'm kinda of at a loss at what everyone means by drilling them out. Second does anyone know the size of the dash speakers? They look like 3 inch to me but i can't tell and I haven't been able to find it anywhere online.

 

If the speakers are riveted to the door metal panel, then the rivets will need to be drilled out so you will be able to remove the old speakers. The remaining holes can then be used with short bolts and nuts to fasten the new speakers to the door. If the holes don't line up with your new speakers, then you will have to figure out whether to modify/drill the speakers' mount or door.
As for the dash speakers, I would measure them to find the exact size, and if you are unable to find the size you need, then I would measure the dash housing for the speakers, to see if the closest size to the original speakers you can find will fit. Good luck

 

I haven't checked back in a while, I decided to just go for it and hope everything worked out and it did. After a few days of work my new audio system is done and it sounds great. Thanks for the advice though.