If Bork were put in via a recess appointment, his age wouldn't be a factor, as such an appointment is only temporary.
Would Bork, once there, be able to be ousted by the Senate if Dubya insists on sending nothing but more hardballs to the Senate that the Senate refuses to get unfilibustered about? I'd think that if 40 Pubbies have enough of a spine they could turn a filibuster around the other way.