For 1969 they did build Chevelle convertibles in Oshawa, and they did build 903 SS396 Chevelles across all body styles in Oshawa. I can't recall having seen the combo you are seeking from Oshawa, but they would have built them.
In 1967 Oshawa built 11 Malibu SS convertibles with L34 power. It is going to be a tough search, Dan.
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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