http://www.crateenginedepot.com/60-L...10580C719.aspx
I got my ls6 from here. they are a real gm dealer. Shipping wasn't too bad for my engine.
The site says the core charge is included so 4300 is the basic cost plus shipping. if you block was ok, which it isn't, obviously it'd be 600 less. That is for a brand NEW engine. and if you look at their other engines, you'll see reman. versions are available too.