was welded in 68 also, why was that ? Noticed it when I pulled my exhaust out of storage for pics. ( sloppy weld job BTY)
Don't know why I was thinking wide ovals ,no coffee in me at the time.
Welded because in production it establishes positioning and it's one less part that needs to be fastened. Might not sound like much but at 57 units per hour it adds up.
On the N10 standard system the head pipes were also welded to the resonators but I believe that was an MVSS requirement. Something else that recently came to light is the original production configuration of the "bright metal" tailpipes. The LH tailpipe was the standard 1-pc pipe; the end of it polished raw steel/flash chromed. The RH pipe was 2 pc welded construction with the tip nickel/chrome. Several original systems still exist in this form.
Remember all this if you see a complete NOS exhaust system for big $. Might be NOS but service replacement components were not identical to parts used in production.