I would look at a set of rods, pistons, and a 6.1L crank if you're looking to stay at a 5.7L displacement but since you're going with a new rotating assembly anyways it never hurts to go bigger. With boost and a 5.7L block I'd upgrade to a 370 so you're not running such a long stroke which will allow you to run a higher rpm to better deal with the supercharger. I would stick with a 5.7L block and don't bother trying to find a 6.1L block, they are expensive as hell these days. Don't forget to get a set of head studs so you can keep the gaskets sealed.
Since you're looking at 15psi, a D1SC or Novi 1500 will work nicely with an early 3rd gen with a ~9.0 CR. You won't need to upgrade the rods to the more expensive I-Beams because you won't be making enough boost to really worry about.
If you do boost then you won't really need to do anything with the heads unless you really want to be making more power; then I'd look at getting a set of ported heads, or going all the way and getting a big valve/ported head. The pre-Eagle heads don't flow that great but they're more boost friendly since they have a lower compression compared to the Eagle head swap that will raise compression to 11:1 unless you run a thicker gasket or get the bowls ported.
