Hi,

You should try any stereo shop that does installs as they should be able to identify the proper wires.
I want to say there is “somewhat” of a standard code system with variations with colorings but Power functions are grouped away from outputs in pairs.
Power is usually a bright solid color like red or yellow while the speakers outputs are gray, white and black is ground. Again those people that work with this stuff on a regular basis know the common everyday in and outs. Like this stuff wasn’t made up just the other day?
You might ask for a patch cord, so they can sell you something! That gives them incentive to help you!
Overall a “coupler” will simplify the hook ups on the car or on the work bench.
This way you can go directly back and forth in the future.
With cassettes, they will always need the capstan cleaned alone with the heads.
These units may have a belt in need of replacement.
With the player at this age and time lag, they may have not gone with a direct drive motor yet?

As I remember, yours still used an eject type mechanization system activated by a lengthy push button. Even older yet, some did not auto reverse during play back!

Nothing like the self those easily ejecting CD’s, of a more modern era, that is now long gone!

I figure out that when they started making “condensed soup,” things were gonna get smaller!
Ahhhh, I may have stretched the truth a little bit there! (:-)

Phil