Don,
I installed a stereo in my ERA, with speakers in the footwells and in the rear bulkhead. I can't remember the exact depth, but think it was close to 2". Bob did provide me with the actual depth.
There are speakers that will fit, and although they may not be the best quality, it won't matter much cause at speed you won't hear much.
I am glad I put in a stereo and even happier that I did not spend much money on it.
