Mounting Fader Switch for Rear Speaker

My first 67 had a reverb unti added to the AM only. I dont remeber where that knob was located exactly. I wanna say right of the radio but not as far as where 68 has a lighter well. Wife agrees that sounds right but not 100% sure either.
The music had a semi concert hall sound but the spoken word sounded like voice from head in a box. LOL
I do remember throwing it away , wiring harness and all.
DOH !