It sure does appear to be some problem with the bumper. As has been said the soft plastic filler strips shrink with age and to my knowledge there is no after market source to replace them. I'm facing the same situation with our 73, the strip is shrinking and cracking too, starting to look pretty bad. I think the best (current) solution is a 72 bumper with the 72 brackets, that's what I'm going to look into this winter, that will eleminate the need of the filler strip.