First off, you're not nuts, just nostalgic.
Second, do they have Iron Maiden on 8-track? That I don't know...
I have a 8-track that the original owner installed. I'm keeping it there just for looks and it does work and I will wire it so that it is operational. Uses brackets under dash. I scored a free box of 8-tracks on craigslist in a fake aligator case so be on the look out for stuff like that. Cool to keep in the back seat.
Firstly, I am no audio/electronics pro.
I have never investigated the wiring. The possibility of just splicing the speaker wires from both units to the same speakers might cause some sort of feedback. It very well may not though. Give it a try and see what happens. If there is feedback, like Bullitt mentioned, Radio Shack used to YEARS AGO, like 30 or so years, sell a switch so you can operate 2 units on one set of speakers. I hooked one up in my dads old Lincoln Town Car for the additional cassette deck in the 80's.
As far as the 8 track wires, my first thoughts are that you only need switched power assuming there is nothing that requires a memory. Also it prevents the issue of leaving an 8 track on and drainging the battery. You didn't mention a ground wire to the unit so I assume there is one. Then there is the power wire to the speakers. How many positive wires for the speakers are there? You mentioned 3 wires. so I assume 1-power, 2-ground, 3-(1) to speaker power?
You radio needs to be hooked up to constatnt power to retain the presets. Dig around with the key on the fuse block with a test light to see what has power and splice in there for the radio. Try to figure out what your spling into. Might be andy to know, like when you don't have brake lights anymore or something.
As far as the speakers go, you can either put 1 speaker, I think it's a weird size, like 4x6 or something strange so it may be hard to find or else some people put 2 smaller speakers together in that one speaker opening. Don't know what sounds better.
