It’s my understanding those were used to remove the engines from the Marysville transport racks.

The racks came in to the assembly plant then the engines were removed and placed on the line, the trans was married to the engine then installed on the k-frame.

Someone forgot to remove those brackets.

All cars were body dropped, no one installed an engine in to the engine bay. Except for repair in the plant and I doubt that happened much if at all.