The 3/4 ton Suburban/Yukon XL was made up through 2013. You can still find low mileage examples, but it does take some time and when you do, they want a mint. I passed on an 07 with 50k miles for $30k. The dealer knew what I was looking for and called me first. I passed and it sold hours later.
I decided I wanted Quadrasteer so that limited me to 2003-2005. I found one in Denver with 87k miles a couple years ago. The 6.0 can handle that weight, but I am not sure the 1/2 ton Burb can. Not that I haven't seen them and Tahoes/Yukons slugging up hills dragging their butts all the way (no thanks!).
