is there a Amp that powers the speakers in the truck, I am going to remove the factory stereo and put in either a alpline or kenwood and don't won't loose the good sound from the speakers.
You can go the route you said or you can wire from scratch with a different system. Most drivers that replace a stereo is because they want higher end equipment. Using factory wiring is not something you want to use in them cases because of the small gauge wire.
If stark just happens to come back around, the amp is built in the unit.
I put an Alpine into my 379. Almost fried it, too -- as it turns out, there are TWO physically identical power connectors back there, but they are electrically different.
As luck would have it, I noticed the smell of burnt plastic right away. I immediately unplugged it and, after some digging, realized I'd used the wrong connector. The stereo survived.
I really wish Peterbilt would've keyed those two connectors differently, though. I still don't know what the other one is for.