'03 silverado speaker size

What are the speaker size's throughout the truck, on a '03 1500 ext.cab. and what is the best solution so far, for replacement of factory head units.

I have an 04 and I purchased a Pioneer DVD5700 Head Unit. The thing has a fold out screen with detachable face. I bought it from Best Buy and they gave me free installation. Any Head Unit bought from there over $99 is free.....so why not take the free install? Since it is a double din, you have many options for the Head Unit, it is all on your preference and your budget. You can go to http://crutchfield.com put in your vehicle info and they will tell you your speaker size........good luck