I bought theses muffles for my 69 Dart GTS 340 from Summit earlier this summer. I too was looking for a aftermarket muffler that was close to the original factory mufflers. So far, I have not installed them as the car is still apart, so I can't report on the fit or their sound.
https://www.summitracing.com/parts/sum-631122-xl/overview/ 2.25 in and out ... NOT stock on a 69 340 equipped mopar.
I assume he is looking for actual FACTORY replacement , Accurate LTD or Gardner will be the only place that has them.
Here is the muffler you are looking for , you may actually want the ACM-18 though , 1 7/8 outlet like stock ... even the 383 and 440 equipped A bodies used that muffler because they used 340 tailpipes .
http://accurateltd.com/A-Body-Factory-Replacement-Muffler_p_198.html
