Early A body HP muffler question

I'm trying to restore a 65 and 66 Formula S to original specs and need some information concerning the exhaust system.
I have a 65, 66 and 67 parts book the information below is from those books


For 1-4 bbl 273......muffler pt#.........extension pipe pt #
1965......................2534468............2534456
1966......................2660541............2660538
1967......................2856245............2823439

I was under the impression 1965-67 273 HP exhaust systems are all the same. (I know a different part number doesn't necessarily mean a different part. I think this is because Chrysler sometimes changed vendor and would change the part number to reflect a new vendor)
Does anybody know why there are 6 different part numbers from the above list?

Over the past couple of years, I have bought two NOS Chrysler mufflers, each supposedly for the 273 HP engine A body cars. Neither were in factory boxes. One has part number 2534468 written with a magic marker..the other has no Chrysler part number. Both have the Chrysler "star", both have the number 10832 (vendor number I think). The 2534468 is dated 1/68 and the other is 10/67.

Both have the 2 1/4" inlet and outlet and one muffler is 3/4" shorter than the other. As you can see in the picture, the big difference is the 1/67 muffler has the inlet and outlet offset but the 10/68 does not.

By now you're probably are confused as I am. Question: Is either or both of these muffler correct for a 65 and 66 HP?

Thanks, Pat