I've installed lots of car stereos over the years and I couldnt resist this challenges of this small space. I Installed 6.5" coaxial speakers in pods on the doors of my 94 hijet. They sound pretty good even with the cheap shallow plastic Boss Audio head unit i got off amazon. Its always the speakers and their placement that make all the difference. Everything else is designed to match and drive the speakers (amps, crossovers, enclosures, power requirements, fuses etc...). I can fade between the little paper cone in the dash and the big speakers in the doors and because that little speaker cracks me up I'm leaving it. might be fun to design a 7th order band pass Subwoofer box to mount under the cab and vent to cab but i would need to measure the trucks acoustics first and It would be lots of math to do though, maybe this winter. Low frequency transducers on the back wall might work well in this location. Has anyone done that? oops, look like someone spilled their pop on the dash panel when it launched from his lap during a brake check. gotta remember to install cup holder and clean that up.Btw where are all your cup holders mounted?