I dont know. You might bend the notches outward toward the bolts. Snug gear screw clamp around it for support and tap lightly? Might have to take the part i=of the column to get a hit at it.
Interesting/puzzling that this backer block is a good size while the other is so small.
I was thinking maybe epoxy a very thin strip of metal in there to see if that would help where it's worn. If it doesn't work at least I could grind it off.