Alan,
On crutchfield when they say there are several sizes that fit, they
mean with an adaptor.They should have some sort of icon that sais fits
or fits with adaptor.The speakers that are in your door are 7"
speakers, and the rear deck speakers are 6x9's. You can put a speaker
that is a litttle smaller but you will either need to buy and adaptor
or make something.
You most likely will need to remove the door pannel. You might be able
to do it with out removing it but i would be a pain in the butt if you
even can.To get to you rear deck speakers, if you back seats fold down
you can go from inside the car or you can crawl in the truck
http://www.cardomain.com/shop is a very good site,they will beat any
price from other sites. their system tells you what can fit and what is
the perfect fit.
Good luck with your system
TroyT.