1965 Dartcharger

Finally the factory exhaust system is back in place. When I took down the old system I found some strange bolt bracket/clips for the bolts on the y-pipe on the driver's side. I have never seen this before. Can it be factory or after market?

I have seen similar style clips for other applications but not on the exhaust as you have pictured. Factory or aftermarket- hard to say after 54 years and other owners!