What is the OEM exhaust configuration likely to be on a '78 450 SEL?

I've seen split manifolds on some of the 4.5 engines. Is it a y-pipe? or twinned pipes down one path under the car? or just one pipe to the rear muffler?

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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