Those headers and that exhaust on a R129 V12 would basically create the perfect car. Every M120 should sound like that.
There is of course the famous video of the W22o with presumably equal-length headers and a custom exhaust screaming like a Zonda or F1 car. If you haven’t seen it, it’s here.
This is the first time I’ve seen a video of a similar setup on a W140. The M120 V12 was, of course, the same engine used in the Zonda C12 and CLK GTR. Naturally it was bored and stroked for those applications and made with slightly upgraded internals. Some S-Classes were built with these higher displacement engines including the super rare Mercedes S70 AMG with a 7.0 L displacement and the even rarer S73 AMG Wagon with the full 7.3 L displacement of the Zonda.
As for pairing a proper transmission to that, apparently some six cylinder S-Classes and SLs came with manual transmissions but those boxes were apparently quite weak and rather sloppy to operate. I suppose a later SL with the 5G Tronic would suffice if you have the sound to make up for it.
(Fun fact: My computer’s autocorrect automatically changes “Zonda” to “Honda”.)