[MDPotter]

The L33 is a good engine! I have lots of advice I could impart on you, but what comes to mind right now is work to that engine before you drop it in. I don't know how many miles are on it, but I would recommend replacing a lot of parts while it's on the stand and easy to work on. I did some of these to my LQ9, but not all of it and am regretting it now:
-Rear main seal - this is what I believe is leaking on my truck now and I don't know how to replace it without pulling the engine.
-Front timing cover gasket & crank seal
-Spark plugs and wires
-Water pump
-Idler and tensioner pulleys
-Power steering pump
-Intake gasket
-Knock sensors and harness (seal the perimeter of the rubber boots with RTV)
-Oil pickup tube o-ring and oil pan gasket. My dad has a 2006 Sierra with the L33 and we replaced this a couple months ago as the oil pressure was pretty low and you could hear the lifters on startup. Not too bad up on a lift, but much easier on an engine stand.

Other things to consider: electric fans, hydroboost (awesome upgrade and not expensive if you go the junkyard route), Vintage Air or keep the factory heat, what route you want to go for the LS wiring harness/computer, any engine upgrades (cam and springs is easy and gets you more power and lopey idle), headers or manifolds (recommend manifolds), what engine mounts to use, what fuel tank/system to use, etc.

I don't want to clog up your thread here, but I'm happy to give you any info on my builds.