Do all stereos use the same connection to hook up?

Ok, I have this old 83 Custom 10 Pickup I'm trying to fix up, and I want to get a different radio for it, so I can hook up my mp3 player. The thing is, the person that had it before me did some stuff, and it has a fairly new radio in it already. So, if I buy a radio with an audio in jack, will I just be able to take out the old one and plug the new one in?

Also, I've got a right and left RCA audio plug behind the seats (from the last guy that had it, no doubt), and there's a red cable that starts behind the seats and goes up right next to the battery, but it isn't hooked up. If I wanted to get new speakers (he didn't leave speakers in it), will I have to look for any specific kind that have an RCA plug, and secondly, how will I power them? Just hook up that wire to the positive terminal and to the speakers?

Sorry for the wall of text, I'm just really confused with all this new stuff.

The RCA plugs and red wire under the seats are for an amp. DO NOT connect the red wire to anything but the power inlet of an amp. The speakers will require sperate wires to power them. The connections for a headunit are pretty much standard - you will need a wire that has 12V power all the time, one that has 12V only when the switch is on and a black wire connected to the metal frame of the car for ground.

Ok, so if I hook up that wire to the positive terminal on my battery, and then plug in an amp, I'll be ready to go?

Will the amp always be on, or will it turn off when I turn off the head unit? Let me rephrase: If I leave the red wire hooked up to the terminal when the pickup is turned off, will it drain the battery?

OH I just remembered, there's also a little tiny wire back with the RCA plugs and red wire, would that be the connection to the head unit?

Last but not least, do you have any suggestions for an amp, speakers and a head unit with an aux connection? 2 door pickup, nothing too huge, just so the speakers produce pretty good quality sound. I was thinking about putting two speakers behind, and maybe drilling out some spots in the door, so one in each door, and then take out the tiny ones in the dash and put in some working ones. So that comes out to six... is that workable? If not, I'll be ok with 4 or 2. As for the amp, I'm not too picky about that, as long as it has enough connections. I have a 400W stereo in my room, and it's pretty loud, but I don't know if that would be too loud or too quiet for a pickup. The head unit just needs to be able to hookup to an mp3 player via aux connection. Single slot, though I could maybe cut out below and make it a double slot.


Sorry again for this wall of text, I just don't know where or what to buy! Thanks for your help!

you will have to look around, most newer headunits have aux inputs for some type of MP3 player or the such.

There is a another small wire that connects to the headunits auto turnon wire and the amps turn on terminal, it will turn the amp on and off with the radio. A good 75 watt X 4 amp should be enough to power 2 speakers in the door and 2 speakers in the back. Be aware that 6X9's or 6 1/2's will not have much bass.

If I get custom front speakers in the dash, will I just hook them up to the head unit? It has speakers there now, but they suck/don't work.

Alright i didn't fully read all the posts so let me advise you on the bit that I caught.

Alright look -
Almost all radios have the same wires but you need to put the wires together. If the person before you did a correct install there should be a wiring harness connected to your cars, with free wires sticking out from it. If he just cut them because he was lazy and didnt want to spend 17 dollars for a harness, then the radio will be connected to that. Either way when you take the old stereo out you will have to undo these connections, and then redo them with the new stereo. It's extremely easy, all you have to do is match up wires of the same colors/patterns. Use electrical tape or caps to seal the connections. The rca jacks that you speak of plug into the BACK of your current stereo, and will into your new stereo also provided it has preouts for subwoofers. Just plug them into the new one when you put it in. At this point your stereo should work fine.

Now -
The red wire you see is a POWER wire for an amplifier. When hooked up it runs from the battery to the trunk to power an amplifier which is used most often for subwoofers, but also sometimes to drive the speakers inside the car. Most likely he did not have it set up like this, and instead of rewiring the car for new speakers, you can just use the wires that the old speakers used. Most of the time there is no need to power in cabin speakers with an amplifier unless you have one kick ass system. As for hooking up an amplifier only to the power wire and being set...thats not how it works.

To use an amplifier to power subs, the power wire hooks into the amplifier from the battery. A second wire of the same size runs from the amplifier to exposed metal in your trunk to act as a GROUND. The rca jack run from the back of your stereo to the amplifier. A blue (usually) REMOTE wire also runs from the back of your stereo to the amplifier and this controls when the amp turns on or off. The amplifier will only turn on when the radio is on. Then there are positive and negative terminals on the amplifier to hook up to subwoofers, and how many and the setup depends on alot of things but its normally just plug and play.

If you have any other questions or i left anything out feel free to ask