I've been searching as to what I have here. my girlfriend bought a 2000 Monte Carlo SS 3 years ago and the guy replaced the engine with a supercharged one from 2003 Grand prix GTP, so he says. I was looking at how to put a serpentine belt back on once and notice all the L67 have 2 belts and L36 have 1 belt. what makes this so special? i was thinking maybe he added a supercharger to the original 3.8 NA and just kept the block? or whats so different about adding a supercharger and only needing 1 belt? ill post pics later but anyone know?

Supercharger snout sticks out further than the accessories.

Though it is possible to put a supercharger on a L36, it'* not feasible without a programmer.

the previous owner did have it programed. he gave a usb stick with HPTuner. I know he adjusted the transmission shift timing. i just thought he said he swapped an 03 grand prix GTP engine and trans. at this point im not sure exactly what he did. anyway of looking up the engine head, block, and transmission code and match it up?
it is a single belt supercharged engine. theres no diagram of how to attach the belt

This is a ZZP SSM90 kit that is fitted to this car. I am guessing it is a L36 with the supercharger bolted on.

I never even knew these kits existed before today. Given that it is custom, you will have to find out the routing through others that have done it. The current route is probably the way to go given the setup, but you will want to look around to confirm that.