Those are belts squealing, tighten them up, or better yet - install fresh ones. I'm also going to guess that the 3G alternator is now trying to charge a partially depleted battery. A single V-belt may not be sufficient to drive that alternator under load.
If you're having difficulty with the engine cranking with a PMGR starter, you need to make sure you have a good battery->chassis->engine ground path. Then make sure your timing is where it should be.