1980 w116 450SEL Exhaust, Muffler, Catalytic and Header Pipe.

['79 Super Turtle]

Hello, I have a 1980 w116 450SEL that is in need of exhaust work. I am looking for information about the layout of my exhaust. I have looked up replacement parts and none of them are like my set up. I know that the center resonator and rear muffler have been replaced, but I "believe" the front pipes and Cat are original. So, here is my question:

All of the replacement parts I can find show a dual pipe center muffler and a dual pipe rear muffler because both head pipes feed into them, but I have a single pipe center muffler (resonator) and a single pipe rear muffler BECAUSE my left head pipe is short and turns 90 degrees and joins up with the right pipe at a union which goes to a Cat and then turns back again towards the rest (AND THIS LOOKS ORIGINAL).

I am wondering if this is because it is a 1980 and for one year they changed the setup? I have an MB spare parts catalog "G" and even this shows a dual exhaust all of the way, but the book might be from my 1979 300SD as I can't find a publishing date.

I can see where a heat shield and bracket for cats left could be in place, but it does not look like the left cat and heat shield and bracket was ever there.

I'm sure that I can come up with something because I have seen left and right head pipes from an aftermarket company and also the dual center resonator (muffler) and the dual rear muffler.

I guess I'm just wondering if this set up is original to the car? Thanks for all and any replies. I have tons of photos which I will post as well.