The 108 front bumper rubber strip has molded ends where on the later 111 coupes the ends tuck in beneath a hole in the bumper, so if the molded ends were cut off it would be too short. a possibility might be using the 108 rear bumper strip that runs all the way across. It could possibly be cut off to length to fit the coupe's front bumper.
When I owned a 67 250 coupe with the early chrome only bumpers, it had poorly rechromed bumpers, I installed 108 bumper strips to hide the wavy chrome finish, I imagine I used some kind of "T" bolts to attach it. The strips looked so similar no one ever noticed the difference