Well, as far as GL auctions, form my exuberance, you can see a lot from the pics, but not everything. My 816 was missing the drive shaft from the trany to the gearbox. Not something you usually take a pic of.
You should take a look at them in person before you bid, and look carefully. They have times about 2 weeks before the end of the auction, to inspect. Some say they run, but most need some help. Batteries are shot most of the time because these trucks sit for years sometimes. All fluids need to be checked. Some times they remove them. Check everything. Don't take anything for granted. I have stood starring at my truck saying things like, "Why the he** did they do that?"
Apparently it is hard to get parts in the military, so these demiled trucks become the parts for the running trucks. It is not that hard to find parts. There is a lot of people here that have parts. There is a wrecking yard section in the forums. if you are talking about the blazers, they are almost the same as the civilian models except the engine.
Another thing to think about is the title. Some trucks sold as scrap can not get a title. If you get a truck that can get a title you have to pay 50$ for GL to processes the paperwork to create the title. SF97 is the form you have to get to title it. It is like a bill of sale from the government. Then you want to talk to some people from your state to get it registered correctly. Mine was going to be 4 times the cost if I had not talked to some people her who pointed me in the right direction. I had to show the DMV how to do it, because they did not know.
So GL is cheaper, but usualy more work. I spent less from GL but I had a lot to fix and then there is shipping to consider.
I bought my 816 for about $3500.
Then I spent $4000 to get it towed out of the base and working good enough to drive home.
Then I bought tires for it because all of them were junk. 2 lots from GL $1200
Missing parts for the wrecker and 50 gal of hydrologic fluid $800
$9500 so far.
Still needs more stuff.
But running wreckers her go for 15k,, so it is all in what you want.