Dual Exaust or Single Exhaust ?

[68Z22]

Trying to determine which exhaust my 1968 Camaro RS came from the factory with,As usually the original factory Exhaust is long gone and had been replaced with headers and after market mufflers and dual pipes.
I am doing a complete restoration and returning it back to factory specs.
The restoration shop raised the question about the exhaust ,single or dual exhaust.
I do not have the factory build sheet to know what it came factory with.
Would the block numbers (327/275) indicate anything,or what about the Trim Tag ,V.I.N.
I have looked in the AIM and can't totally make sense of it.I have been told that certain holes in the rear frame rails can determine which exhaust it came with.
Any feed back would be greatly Appreciated.

[Sauron327]

http://www.camaros.org/diffs68.shtml

[plumL78]

If it doesn't have the factory well nuts in the left frame rail like the right side does then it was single exaust