I have the rear speaker option in my '68 'vert. (and yes, only one speaker was the option, the radios could not power three speakers). With the top up, it relatively works OK. With the top down, its useless.
Another cool, somewhat unusable option, common on these 'birds. I generally have the fader turned fully to the front speaker, thus not using the rear much at all. 98% of my 'vert driving is with the top down.
It looks just like Stealth's picture, and yes, '67-'69 are the same.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold