Re: single to dual exhaust hanger mounting
Don't know if the hangers are available (probably repops), but the holes shown are the hangers' mountings for the transverse muffler. They are located in the trunk pan reinforcement channel that runs between the shock mounts. My '67 has the same tapped mounting plate and rivnuts at the other side at this location, but the reinforcement is slightly different (no relief dimples at the reinforcement for exhaust clearance). Hope this clears it up for you. I can send a pic of the original pan (which I have removed) showing the details - if you need it.