I installed 6x9 3 ways in the area under the rear side glass. There's enough room ,just have to cut the metal away! Have 4" 2ways in the stock front location & the 10" sub in the rear of my custom console.
i have 2 6x9 speakers and 2 6.5speakers i have a video of my truck and it shows my speakers http://www.youtube.com/watch?v=Z0RULmGnBdA&feature=channel_page
I put 3 jl w-6 12's in a sealed box behind the seat of my 85 2wd. built a 12x54 inch shelf to replace the cardboard one, bolted it into the stock side brackets and braced it in the center. Then built a box 13 inches deep on the bottom 9 inches deep on the top, 53 inches wide and 18 inches tall using 3/4 mdf came out to around 1.3 cu ft per sub. Just enough! mounted the jl 500/1 vs amp under the rack on the driver side and still able to mount the jack in stock location under passenger side. It gets the job done.
Put 6 x 9 three ways in boxes on the rear shelf to go with upgraded 4 inchers in the dash. No bass, but full mid to upper is there. Looking for a powered sub now.