Seeing as you've already got the 4.7s, I'd go with the cage. Having dumped my truck over more in the last year or so than in the whole time I've wheeled it, (and flipping my DD last march), and seeing the results of not having upgraded cab support, not having a cage makes me a little nervous now. with the 4.7s, you're in pretty good shape for crawling now, so I'd get the cage now, ensuring you can buy the duals later
DD:
http://board.marlincrawler.com/index.php?topic=37481.msg701832#msg701832
