Go for the LS6. If it costs you $1000 more for the additional 65 hp it will be worth it. Try for a 2002+ model for more HP and cam lift. A used set of LS6 heads would cost you $1000 used. A LS6 intake will cost you $325 used. A LS6 cam would be at least $100 used. All that to move the hp up from the stock LS1 to an LS6.