I bought a Mitsubishi Electric factory radio on eBay a while ago. It came without any wiring, connector plug and was missing some of the control knobs. Didn't know if it worked.
After a crap ton of research, I found a plug that would work on the connection at the back of the radio. It came with wiring, but it wasn't pinned for this unit. I never found a wiring diagram after hours of searching. I did find a picture of the same radio in an '82 Mitsubishi Sapporo which gave me a clue to when it was manufactured.
I took my multi meter and traced all of the pins to speakers, power and illumination, the re-pinned the plug correctly. That was fun - no.
I connected to a 12 volt power source and found that the damn thing worked!
I went to a local Goodwill store and bought a set of high end Yamaha box speakers to use as a temporary set up until I can find some factory door speakers and possibly pre-cut factory door cards. I don't want to hack up the current door cards - they're mint.
The radio actually sound excellent through the Yamaha speakers and fit up against the bench seat firing right towards the driver/passenger.
The radio fits in the exact location where the AM unit was and bolts in the same way.
I'm trying to keep this rig as close to original as possible with good upgrades and factory optional parts.