While those look very nice, they don't appear to be for a merged exhaust. I still have my original Fortuned dual quiet pack exhaust from back in '84 although I cut off the bell tips. It isn't a merged system either.
You are indeed correct.
Its not a problem for me as I think a merged header would be a bit overkill on my 1300 mouse motor!
The new range of CSP mufflers are very nice but a little out of my price range.