I'd like to find the optional OEM 8 track for my 69.
Years ago I got an extra door for the right rear compartment and stuffed it full of stereo with the stereo facing up through the door. I cut a speaker board that was the shape of the rear wall, it just slid in flat and sat right on top of the hump all the way in the back but about 5" from the back all. I cut holes in the board and put the biggest Mid I could find on it, a couple of tweets, covered the holes with some wire mesh and put black speaker cloth over the whole thing. I pulled the rear compartment light and mounted it on the board and put some long wire on it. It sort of just hung there, I didn't attach it at all. It never moved, the way the back is desiged it sound great so it didn't need a box or insullation. It was just a speaker board. To easy. I upgraded the stereo to a Sony Disk Jockey but once my hearing went to Poo I took it out. No permanent damage (to the car), just the snipped wire for the rear light. That's all back to original now though. The best part was, with the board all the way in the back and the light mounted on it, you couldn't see it and it looked bone stock.