looking for shoulder belt attachment location

This is a Fastback! But the hole should be close on the notch. The belt attachment is just above the door glass to rear glass location you may have marked as the coat hook. On a Fastback the coat hook is further back and only a small hole for the stainless screw to attach it. Hope this helps! The 68 may not have the bung for the belt attachment as you have previously read in the older posts. Others have welded in a blind nut.

edit

Your pic may be correct for the belt mount in the location you marked as the coat hook, and the small dimple behind the open hole you marked in green is for the coat hook. Not sure as I never had my old 68 notch down that far to confirm.

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