No word yet on who will get the last spot on the team, but I'd have to think it'll go to Eric Hinske. Freddy Guzman was barely used in the ALCS, and now with the pitcher hitting in at least two games, a good pinch-hitter is more valuable than a pinch-runner.
Or maybe Joe throws a curve and drops Frankie Cervelli in favor of Guzman and Hinske, but I doubt it. With Molina catching Burnett, the Yanks need a third catcher in case Posada (who will replace Molina mid-game) gets hurt, plus Cervelli is fast enough (not just for a catcher) that he could pinch-run if needed.
Guzman only got into two games in the LCS, didn't steal a base and got one PA (he struck out). In the regular season, he only got seven PA, but was successful four times in five attempted steals. Hinske hit .226/.316/.512 (in 98 PA) after coming to the Yankees in a mid-season trade with Pittsburgh. The answer seems pretty obvious (but watch: because I wrote that, the Yanks will desperately need a pinch-runner multiple times in the Series).