Walker Muffler 21691, what's it fit?

[GSGregg]

If anyone still has a Walker catalog circa 1979, I'd like to know what a 21691 fits.

In 1979, I bought dual mufflers and tailpipes for my 1966 Skylark GS and replaced only the blown out, right-side muffler and tailpipe; the left-side pieces are still holding up with 475,000 miles, believe it or not!

Anyway, several years later I considered installing the rest, and found out that the muffler I was sold for the left side was incorrect! I looked up the correct listing, but have long since forgotten it.....I think it fits the left side of a fullsize sedan or wagon from GM, but that's as far as my memory goes.

Thanks, all!