As i further Read up and now may have a better understanding ( maybe ) , Jason's Tape Player will have the
TOYOTA Factory Radio Speakers FED into it first , then out to OEM speakers
this way when a Tape is inserted the AUX in this case TAPE , shuts off the RADIO FM Or AM SIGNAL and Routes...
have u seen the Vendor, on EBAY that sells OEM TOYOTA Radio Literature Copies ?
I really hope this is your Book u need ............ :)
https://www.ebay.com/itm/1970-1975-Toyota-Installation-Manual-for-Car-Radios-and-Tape-Players/311952813922?hash=item48a1d62f62:g:UTMAAOSwr4Zb1OLm
Hi Jason
I have a 8-Track Player Hook Up Instructions i will post FSM INSTALL Manuel :
Tell Me if what pages chose to help u make any seance ?
its a Magazine thick OEM 8-Track instructions TECH Thing ........
:)