I do LS swaps, all the time. Literally all the time.
There isn't a day in the week where 500 bucks doesn't get me a complete 5.3 with accesories and harness dropped right in the bed of my truck without turning a bolt.
They're so common and cheap, I won't even pull one in the junkyard for 250, because usually I can just buy them in the 3-400 range. 500 is the, I gotta have one right now price.
The 4L60, worthless to me, but to a guy with a bad one, another 400-500 bucks.
1200 is a deal, run