3800 Series 2 engines all have cast rods in them just like your GN motors. The 3800 Series 3 engines came with powdered metal (aka: PM) rods (some early production 3800 Series 3 engines still had cast rods). The word in the community is the cast rods are good to 600hp and beyond and I haven't heard much different about the PM rods.
As with anything else, the no.1 killer of connecting rods is excessive RPM. Size your turbo right and you'll never need to rev it past 6000 rpm to make good power. Some guys have revved these engines past 6700 rpm but I really see no need to do that on a turbocharged setup.
The 3800 Series 2 and 3 engines all have the same FWD GM bellhousing (same as 4cyl [exc Quad 4], 2.8/3.1/3.4 V6, etc). So your 2004R trans will not bolt up to it. The 700R4 and 4L60-E that came with a 4cyl or V6 (except 4.3L) in the S-10's and F-bodies will bolt right up to these engines. The OBD2 PCM from the 1998 Camaro/Firebird 3800 can be tuned to work with a Turbo and will also control the 4L60-E. The only thing you need from the Camaro is the flywheel/flexplate, oil pan, mounts, and intake. You can use the heads, but they are the same as any other FWD non-supercharged head which may be easier to find. The SC versions of these engines have thicker/stronger connecting rods, pistons, and piston pins. The N/A versions of these engines got lighter duty versions of these parts and also higher static compression due to the less dish in the piston. SC and N/A versions of these engines got the same cast crank, but the balancing is different due to the difference in weight of the pistons/pins/rods. All Series 2 and 3 engines are externally balanced, and the amount of counter-balance built into the flywheel/flexplate and balancer is different between SC and N/A engines. So if you mix and match parts (use N/A parts on an engine with SC internals), getting a rotating assembly balance job done would be a very good idea. Some people have been able to make some good power on the N/A internals with boost and that higher compression (9.4:1), but a lot of people have melted down those engines as well.
The SC's parts being stronger will put up with more abuse (and also the lower compression of 8.5:1 is more boost friendly); but there is still a problem with stock piston design. GM designed these pistons to be more emissions friendly by moving the top ring land very close to the top of the piston (on both SC and N/A pistons). This creates a problem where the top ring is exposed to more heat vs. a performance design + the factory ring gaps are quite tight. So if you are going to use stock parts, I recommend you file the rings to give yourself more gap at the very least - this will help some but still does not fix the design problem of the piston. The stock pistons are cast for both SC and N/A but the SC pistons were coated.
If I was going to build one of these engines up for use with a serious amount of boost, I would throw away the stock pistons and replace them with forged units from a good piston manufacturer and properly set up all the clearances. I feel the stock rods would be fine for what most people would be doing with them and the only thing I would change is all fasteners - replace with ARP brand stuff. Nothing wrong with the stock cast crank or stock cross-bolted main caps either. The stock head gaskets work well too, but I have heard bad things about FelPro head gaskets on these engines so you may want to steer clear of those. There is also no reason to do anything with the factory oil pump. It is a gerotor type pump that puts out more than enough volume and pressure than you would probably ever need. All the turbo builds I have done using these engines produce a minimum of 40psi of oil pressure (full synthetic 10W30 oil @ hot idle) and usually produce 70-80psi of oil pressure above 2000 rpm.
About the only other bad thing I can think of with these engines is the factory timing chain. It is quite small so you can't really use a big cam that requires heavy valve springs with it. And all of the aftermarket chains I have seen that are stronger require you to remove the balance shaft which will require you to plug some oiling holes in the block. I have seen some aftermarket timing chains for these engines go on a bit tight which wipes out the front cam gear quickly - so make sure you check yours if you change it and make sure it isn't too tight.
-ryan