It's a sand toy, HP is king. You're going to be disappointed to spend $2k+ and all that effort for "only" 300hp.
Go 6.0 for sure. Also while you're checking around call Kevin at Pacific Fab. He's a friend of mine and they are heavily involved in the LS marketplace. They have another company, Tilden Motorsports that deals with all of this stuff.

I'm gonna get one of their new intakes when I put the cam in my SS
x2 for $200 dollars it shouldn't even be a debate. rpm is king in the sand, but smooth controllable torque off the line gets you rolling without just digging.For only $200 difference, it would be stupid to buy the 4.8.
Martin
(I understand with paddles its less of a concern, but still $200 for an extra 25hp? people spend that much for less all day every day)
MuddySub put one of their turn key motors in his suburban. Check out his build thread
EDIT: here's the link- http://coloradok5.com/forums/showthread.php?t=287329
I knew he did and I think, colbystephens either did or was planning on it as well.



