FYI, it's not a double DIN opening, it's a DIN and a half.
I just went with a singe DIN head unit and the adaptor to hold it in, carved that up to fit my CB and all is well. My Ranger sports a Pioneer 7600, but once you pop the faceplate off, it looks just like the 3500 that's in my one BII, so thieves have no idea if it's a cheap or expensive one when the faceplate isn't on.
It's not easy to put subs and such in a supercab and still have full use of the rear seats. IMHO, probably the cheapest and easiest solution would be to put a single 12" sub in a truck box and fasten it to the rear wall of the cab in the middle, then throw a towel or something over it.
I had a car box with a pair of 12's in it behind my seats for a couple years, with it laying down like it's supposed to, you couldn't tell what it was behind the seats, and it made a fine table about the same height as the center console. Downside was you couldn't use either jumpseat. Then I stood it up on end behind one seat, and that would allow someone to cram in there on the other side, but it wasn't comfortable.
I've seen people build boxes in the jumpseat wells, but I use those to store stuff like a jack, jumper cables, MRE's, bottled water, other survival gear.... I don't really want to give that up if I can help it.