don't go past 20 you risk damaging the block

Just a quick correction..the heads are not "exactly" the same. The difference is two extra holes in the intake manifold flange that pass PCV to the intake manifold. You can add them to the N/A heads by carefully drilling them (use your SC heads and the gaskets as a reference to locate the holes.) This is one of those deals where GM used the same casting, but did a little different machine work to them. You don't have to be exact on the hole sizes, it'* just to route the crankcase blow-by into the PCV system. If your care full and start with a small drill bit, you can even do this with a hand drill.

The rest is true. The block and crank will interchange. The rods, pistons, and balancer should be changed to the */C specific parts....or run the N/A parts on a lower boost level (to compensate for the higher base compression of the N/A motor.)

Compression is no different between the L67 Series 1 and the L27. They are both 8.5:1.

Ooops. I stand corrected. I guess I'll go crawl back under the Camaro and keep my yap shut.

Yeah...just when I think I have a handle on the particulars on each revision of the 3800, along you guys come and blow one of them out of the water.

(Back when I was contemplating doing the top end swap on the LN3 using a M62 SC, I kept finding two part numbers for the heads...one specific to the the SC, one for the NA..so I figured they came from the factory that way...NA'* without the PCV, SC with the PCV. Had I realized the NA L27 came with the holes in the heads too, I would have yanked a pair in the local yards instead of working around the PCV system.) I think I'm going to take a few tylenols and go climb back under the car.