I don't know, but I wonder if it could be a production GM vs. service replacement GM part? If the car ever got tapped in the back in the last 53 years...
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67 Chevelle Malibu Sport Coupe, Oshawa-built 250 PG never disturbed.
In garage, 296 cid inline six & TH350...
Cam, Toronto.
I don't judge a man by how far he's fallen, but by how far back he bounces - Patton