6.0 and ls1 are the same basic block, everything will work, you do have to drill and tap one hole for the alt, but other than that it will go right in. what year 6.0 early iron headed ones had a different crank spacer.
I havent gotten one yet, I was just wondering what it would take to swap it in... I think the current motor is living on borrowed time right now so I'm just looking at options on getting another motor. It'll prolly be a newer one, like 2001 or 2002+. Wasnt it the 99's that had the iron heads?