Believe I have the answers to your questions. Although my time is at a premium, I find these posts interesting, as it raises new issues and ideas for my on-going research. I created the first and only on-line guide to the Chevelle audio world:
as well as provided essential radio research material to Mr. Alan Colvin in his latest and greatest work "Corvette By the Numbers". I've also restored vintage GM radios. My research is always
on-going, as I try to untangle the mystery that is stereo/multiplex/tape systems in post 1966 model year Chevrolets, focusing primarily on the Chevelle line.
To cut to the chase, yes I DO
believe you could get the following in a 1967 Camaro;
An AM/FM stereo-multiplex radio AND an 8 track player.
This system literally was "thrown" together at the dealership when requested, and designed as an after-thought as far as the Delco engineers were concerned. Will post pictures of units (but not the installations) if/when I get the time.
This system utilized an ultra-rare
switch. It was a small round "knob" that hung under the dash. It had a bracket that said "RADIO - TAPE". By turning the switch, you literally switch ALL of the power/speaker connections to or from the standard 4-knob multiplex control box OR the tape player which also had 4 control knobs to the 4-in vehicle speakers.
This was done to allievate dealer stress, this little switch linked "the two worlds". Both the traditional below-dash tape player and the below dash multiplex would normally not be founding "working" together, but they were out of necessity when the dealership needed to install a tape player when Am/Fm multiplex was already there. I've even seen an image in a dealer brochure (an artist's rendering mind you) showing something that totally blew my mind the first time I saw it. It showed the 4-knob MPX (multiplex adapter) STACKED! on top of the 4-knob tape player and the whole thing secured to the bottom of the dash.
I can not gurantee my findings 100%, however I just consulted my Sams Photofacts and my 1967 Delco manual, and the evidence seems to support what I have said. I do have a saved image of the rare mpx/tape switch (somewhere in my mounds of floppy disks of radio images!). The switch DOES exist, although I can not say it was used in a Camaro personally. Finding this switch is next to impo$$ible. If I ever find one, I will not sell it.
Interestingly enough, the Chevelle line (thus far) appears that if one ordered a am/Fm radio with multiplex stereo AND requested an 8-track player, the factory did a NICE job, thus installing a model 7300491 multiplex stereo adapter INSIDE the dash (this unit has no control knobs) and was linked to both the am/fm radio AND the typical 4-knob 8 track player (7300481) via cables. When the radio was tuned to an FM-stereo station, an indicator lamp IN THE 8 TRACK lit up "FM STEREO" controlled via the "hidden" mpx box (7300491). When an 8 track tape cartridge was inserted in the tape deck, the internal switch mechanism disabled power to the radio and mpx adapter as well as disconnecting the speaker loads from the radio's output and "reconnecting" them to the 8 track's output. Power was also applied to the 8 track, causing another indicator lamp on the 8 track to lite "STEREO TAPE". What was nice about this set-up was it took advantage of the technology (after all, it was FACTORY specified/installed) and required no manual human interaction when playing tapes (no little switch to switch under the dash).
I hope this helps. Please do not take everything as gospel--yet, I'm still doing confirmation work. The research on this "stuff" is very rewarding, yet tedious and time-consuming. I ask that you please do not e-mail me
due to time constraints of already answering many, many radio questions for others.