Speaker Size on NC1

I have some speakers that were set into the rear parcel shelf of my old car. I had a look at the speakers in the doors and the ones I have are smaller. I was hoping to get a plate made up to cover the extra space (ie mount my speakers to plate and mount the plate to the standard holes on the door). what size are the standard door speakers in a NC1 (non bose)? 

 

Thanks

what about replacing the speakers in the rear bulkhead if they are better quality?