Well Timid do not forget to plan ahead with your installation and research what has to be done to get the job done that you want. Not all installer are in the know. Any way
use these adaptors from www.partsexpress.com
to resolve your 6X9 loudspeaker depth problem: Metra 82-4200 6X9 to 5X7 hole adaptor. Also do not for get that 6X9s do generate more bass and so will excite vibrations within the door panel. So do not forget to get yourself some vibration damping like dynamat and foam 6X9 speaker Baffles to stop the back wave other speakers from rattling the glass metal and plastic back their and do not forget to stuff that flexible baffle with some poly-Fill stuffing
to increase the size of the baffle area. Simply dropping in a new driver is just not enough if a higher quality sound is what you are looking for.