Montana is the best pure quarterback I've ever seen, but the Niners did have some pretty good players on the defensive side of the ball in the 80's. Fred Dean, Hacksaw Reynolds, and Ronnie Lott jump to mind. The offense usually managed to break other team's hearts in the last minute or two of the game(Bengals in the SB, the Saints everytime they played, etc.), but their defense wasn't shabby.