hello, pretty sure the sizes are 6.5" for the doors and 4x6" for the rear but to confirm you can go to crutchfield.com and click "out fit my car" and it will give you sizes and options on new speakers.
1988-1999 Chevy and GMC full size the door speakers are six and a half inch on the extended cab the pillar speakers are 4x6 in. Some Silverados also had a small tweeter inside the door.
It has 4x6" speakers.
4x10 rears
All the speakers in a 1991 Chevy Silverado should be 4x6 if they are stock.
I believe its 6 and 1/2 inches and for the one on the arm rest on the door a 4 by 6inch
6.5" round speakers.
Front Door Speakers are 6-1/2"
Stock speakers should be 4x6's
4x6
4 x 6
4×6
The door speakers are 6 1/2 " round...still looking for the size of the rear ones.