Ok, I started working on Bronco Speaker Placement in 1982.... I've had mids in the doors, and the Door Panel drilled out to look like a speaker grill. and (Back Then) 6x9's in the rear side panels. Best I did, was move my Fronts to the Kick Panel, and Yes, the back of the speaker was Outside, I had Foam baffles on them, Worked great.
this time around, I'm welding 1 lb coffee cans in, cut down, about 3" deep to the kick panels and installing 4" speakers there (Bedlined of coarse). a Free Air 8" sub in the forward Rear Side panel (Directly across from the gas tank vent) and 5x7 mid/high towards the back.
Main thing is NOT to mount speakers anywhere flimsy, you'll lose bass by vibrating metal instead of throwing the sound. My F250 has all the speakers mounted to 1/4" plywood.
I'm working on a Lower Dash Console, that will hold my iPad. And most Quality Head Units (about $150) have AUX in and USB to charge the iPad. the iPad (or even iPhone) is a great way to store MP3's, a 9.5" GPS Screen, Movies, and Internet while away from Home. and, the Top of the line iPad, is 1/2 the price of adding NAV, DVD, and MP3 Storage to a Car/Truck (See youTube, search iPad + Tacoma, check out "SoundMan" in Santa Clarita Valley)
I disagree with mounting Speakers in the Doors, because I got a wild hair, and ran Roadster Doors in the Summertime when I was a Kid. That bronco had 4 or 5 different Woofer boxes across the back over the years.
My BEST Woofer Box EVER???? I put in my CJ7, the Box's Face was inset, and Angled, and the Woofers fired DOWN onto the Floor. It was the only way to keep the Bass in while on the Freeway with the Top Off....