@JM in KY,
I have a Delco AM-FM 8 track combo but haven't installed it yet to see if it all works. I bought it off of Ebay and the seller said it all worked with no problems. If you get one of those the wiring is the same as far as power is concerned, the wires for powering your AM are the same, black, yellow, gray going into your plug in your radio, and if your wiring has the extra wires for sterio speakers even if it's just a left and right up front you won't need any additional wires to hook it up. There are plug-in's in the back of the radio/player for the speaker wires.
I used to go to estate sales some years ago, and occasionally I still hit one or two. I got on this kick of picking up 8 track tapes whenever I could find them, which wasn't very often. You have to look at them very carefully as for the condition, and even then they can look good but have the tape messed up inside. But I have a couple three dozen good condition tapes from the era.
Sometimes you can tell if the tape might be bad especially if the paper label is worn in certain ways that looks like it was put in and out of the player fifty million times and is worn nearly off. Don't even buy it if it looks worn at all. But if the label is in good condition you have a better chance of getting a good tape.
Just understand that a player can eat a good tape before you can even reach down and take the thing out. It can also be a bad tape to, the tape is to loose that will cause the tape to get hung in the drive wheels inside, so a lot of times it's not the player, it's the tape.
Cassette's were a bit easier to deal with if something went wrong. You needed a ordinary pencil and you could stick it in the drive cog you could see on the tape housing, and spin it in one direction, then the other and most times that would fix a tape that wouldn't play.