Can LaHair play anywhere but first base? I wouldn't mind seeing if he could be decent enough with the bat to be a nice bench player, but it might be nice to have more flexibility defensively.
Montanez is a career .223/.257/.323 hitter at the major league level. That's basically Zambrano with less power. As JR pointed out a couple weeks ago...nice for a pitcher, but not what you want from a position player.
Bobby Scales is having another typical AAA season for him, and has hit .248/.342/.401 in his time the majors. He's probably the best choice.