Ben, I think the core support you are showing might be from a Chevy engine car because you are missing the tab that would be spot welded in place for the battery hold down. With a Pontiac engine the Charcoal cannister is mounted on the passenger side with a metal hoop that wraps around the cannister and bolts to the subframe with two bolts. Here are some pictures I took during disassembly of my 1980 TA with a NA 301 Pontiac engine. I never had the u-nut installed.
IMG_1559 by
Lawrence Alexander, on Flickr
A better picture with the core support removed from the car, but all hardware still in place.
IMG_1558 by
Lawrence Alexander, on Flickr
