The floorpan is dimpled in the location for the passenger side bracket! They were not drilled unless the car was dual exhaust equipped, but they are there! Ill see if I can get a pic for you when it's light out! Geof
I finally had a chance to hunt for the dimples in the floor pan & found what appears to be 3 of them in the area where the bracket would go. Unfortunately they don't line up with any of the holes on the bracket itself, so I am hunting for a photo of the underside of an A-Body showing the bracket. If I don't find any photos I may just wait until I go to Carlisle next week & ask someone with an A-Body that has a dual exhaust system to let me crawl under the car & take a look.