i just recently put new door speakers in a 2000 Chevy blazer. They are 6 and 1/2 in all four doors.
google caraudio and find a website that shows fit of your car
To change the front speakers, you will have to remove the door panels to expose the speakers. Once exposed, unhook them by disconnecting all the wires.
Tucked into the quarter panels on the front of the car
The front door panels have 6 1/2" speakers and the rear speakers are 6x9"
Remove the door panels
I JUST LOOKED IT UP TODAY THEY ARE 6.5-6.75 IN. SPEAKERS
For the front speakers you need to take off the dash pad and the rear speakers you need to take off the rear speaker panels.
The 1988 Chevrolet Blazer front speakers measure three inches by four inches. The rear speakers measure four inches by five inches.
In the front
Unscrew door handles in front first then just pull off door panels carefully unscrew speakers and replace with new.