I've been running an LS3 in my 2007 Avalanche since 2015, it replaced the original L76. I had multiple broken exhaust bolts on the 6L and was looking at pulling the heads to correct. At the same time I was dealing with minor leaks at the rear main seal and oil pan gasket. With around 125k on it at the time, I was also worried about AFM lifter failure. The labor and cost to address all the above made the LS3 swap a no-brainer. I sold my L76 for $1800 and the buyer/friend included a tune for the LS3. I went the LS3 route since I was able to "delete" AFM and VVT without having to pull a head bolt. I added a cam, converter and longtubes as well. I ended up with a brand new engine, and no AFM to worry about for not much more than what it would cost to address the issues I was having. I did blow the stock trans on the first drive (and twice more thereafter), but I've since addressed that as well.
I believe I have a word doc with all the parts I used if you have any specific questions. Off the top of my head I did need a 3-bolt cam gear, MAP adapter harness, I had to adapt the knock sensors, I used a Camaro water pump and tensioner, and needed to adapt a few accessories for belt routing. I did a ton of other maintenance while I was at it like motor mounts, etc.