Guess you have already checked the MPC to get the part numbers. Don't think your going to be able to find assembly line parts or at best I don't think anyone is reproducing them well. This leaves you with used or service replacement mufflers and tail pipes which are going to have different dates and may be slight different in design some way.
Believe that the items were the same as the 69 428CJ Fairlane/Torino parts. Sorry if I'm incorrect as I've only owned one Talladega
Looking at the last MPC they show that by these parts had already been replaced and were being serviced by D0ZZ-5032-R (mufflers) and D0OZ-5255-G & D0OZ-5255-H (tail pipes) parts
You will need to find someone with a 1969 MPC copy that covers that section. Its found in the text, not the illustrated pages, of the manual in section #52. Have part of a Aug 68 MPC but not that section