Good pictures, does idler arm move, is it bent, loose, cracked? QUOTE]
It would be a good idea to check to see why the pulleys top lid was worn off in the first place. mechanic mark asks "does idler arm move, is it dent, loose, cracked?" I think he's looking for the reason for the pulley damage (top lip worn off). You might check the alignment and/or side to side movement of the idler pulley or the part that holds the idler pulley so you don't have the same problem with the new pulley. Maybe you could let everyone here know what you find. Good luck with your Murray.....