Pretty much anything from 99-up are good. The newer the better. If you plan to open it up and go through it with new bearing and rings any of them with reasonable mileage will work, and by reasonable I mean under 200,000.
If you want one to drop in, get ones with low mileage (less than 60,000), but again, if it runs you still will be fine. The top of the line 6.0L's like the LQ9 are going to be more as they made more power, but a cam change will immediately wake one up. If you get it, make sure you get a pull out where they remove everything, engine, wiring, ECM, ETC and I recommend getting the trans with it... Avoid cut harnesses unless you plan to purchase aftermarket harness.