The bumpers themselves are the same width, but the brackets will be in a different place - attachment to Chevy frame vs. Pontiac frame - so you would most likely have to move the brackets.
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Hillar
1970 LS4 (eventually an LS5) Laurentian 2dr hdtp -and a bunch of other muscle cars...
I think you will need to fabricate brackets, there will be no OEM part for this swap. It`s one of those deals where you need to get the US bumper, take off the Canadian bumper and see what you are up against first. Maybe you can modify one set of brackets or the other, maybe you will need to make up fresh ones from scratch. Best to have the US brackets in hand as well.
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Ray White, Toronto ON
Formerly - The one and only 1973 LeMans 454 "Astro-Jet"
I recently put a complete 70 Bonneville bumper on my 70 2+2. To my surprise, (for 1970 anyways) the bumper bolts to the body with 6 bolts, not the frame. So even though the Pontiac frames are different than our Chevrolet ones, it didn't make any difference. Not sure about 1966.
Before I started, I used this reasoning: The Catalina and Parisienne had the same bumper, but the Bonneville had a different bumper (wider tail lights & endura insert). I however had seen a Catalina with a Bonneville bumper, so I figured I could also adapt. I had no issues.