The upper should be SGB, the lower interior color. The lower should have a rubber isolator pad glued in place, see the attached pic. I don't recall if the SGB upper has the pad or not. I can check later if nobody chimes in.
I'm getting a bit confused here!" :-)
Firstly does the 68' even have a lower bracket per your picture? I know the 67' does, but there was no such bracket on my car, nor can I find a picture of any 68' column with one attached. Also P-5770 of the factory parts manual, which shows the 68' fixed column, shows no such bracket...
When I was referring to a lower bracket it was the firewall to column bracket (2 piece plate), because as far as I can tell that is the only lower bracket fitted to a 68' Just asking! here to learn etc. It wouldn't be the first time a piece was missing from my car! :-)
Secondly as pretty much every photo I can find of the dash undersides / columns in 68's shows that big upper bracket to be interior coloured, not SGB.
So is the black interior version unique in that it gets SGB rather than DCM?
Also Jeff, not wanting to draw this out. But in your second photo of a brown coloured column the firewall plate is SGB, is it not?