The sequel -this is what these brackets are for.

[Bob Sawyer]

I finally found a reference pic of the mystery brackets. Back when I started on the restoration, I disassembled the exhaust hangers to be blasted. I ended up going with the Accurate Exhaust system which included the hangers. These brackets were hanging up in my garage.
Mystery solved!

 

[dadsbee]

HA... I knew I'd seen them before and couldn't put my finger on where. Not being on a hanger/rubber was the throw off..