Oh, did we forget to mention that the Mustang V8 under the hood is also supercharged, and was fitted by Roush?
If this writer had a nickel for every Mercedes-Benz W123 wagon with a Ford engine swap that’s cool enough to write about, he’d have two nickels. Which isn’t a lot, but it’s weird that it’s happened twice, and in such a short span of time no less…
See, shortly after covering the wild Barra-swapped Benz up in Finland that could supposedly crack 200 mph, another eyebrow-raising W123 popped up on the r/SportWagon subreddit. This time, it was a brown 1985 300TD, which where once a clackety old diesel under the hood, now sees a 5.0-litre supercharged Coyote V8 shoved in its place instead.
Oh, and it is not just any ordinary Mustang 5.0 either. This one’s been lovingly tickled by none other than Roush!
Now, ordinarily, you wouldn’t expect the Mustang maestros at Roush to have anything to do with a vintage diesel Merc wagon. But apparently, if you’re a friend of the company and show up with an oddball project and enough enthusiasm, they’ll get intrigued.. and perhaps just a little carried away.
Thus within a month of the being dragged out of its extended hibernation in a barn, what was supposed to be a straightforward restoration of this old Merc quickly spiralled into something a bit more… unhinged.
Someone at Roush figured out that, with a bit of encouragement (and a discreet hood bulge), a Coyote V8 would just about squeeze into the W123’s engine bay. So naturally, in that went. Also, because “subtle” isn’t in Roush’s vocabulary, a supercharger got bolted on too, giving rise to the “SC” bit in the newly-christened Roush 300TD/5.0 RSC.
Sending all that sweet supercharged power to its rear wheels is to be the responsibility of a Tremec drag racing transmission, while keeping this brown Benz composed through corners falls to a set of Mustang KW coilovers mounted on custom-fabricated brackets. And all of this then is brought to a prompt stop courtesy of massive Wilwood brakes, which are to be found hidden behind a set of standard Mercedes alloys (albeit from a very different Benz) for that intentional sleeper look.
In fact, aside from said larger wheels and a few subtle badging tweaks, this brown Merc looks pretty much the same from the outside as it did before it arrived at Roush. Even its brown interior is a reupholstered version to original standards, with a stereo head unit and speakers (plus a couple of cheeky new gauges) being the only mod cons found within this 80s long roof.
The only indication to someone not in the know that this Merc is something special is when the Coyote roars into life, as the low V8 burble emanating from those twin pipes poking out from its rump is really a far cry from the clatter of the original OM 5-cylinder oil burner.
As cool as the mechanicals are however, what truly makes this build truly special is really its backstory.
The current owner — Redditor u/captainklaus, a self-proclaimed wagon fanatic — has had no shortage of long-roof legends through his garage. This includes E39 Touring converted to M5 spec, the latest and greatest G99 M5 Touring, plus a string of Audi Avants, Volvo estates, and even a CTS-V and a Subaru long roof thrown in for good measure. But this brown Benz seems to certainly hold a special place in his life.
“The car had been owned since new by my parents, originally bought in Germany in November of ’84 through a US service member discount program. (More potentially boring background: my dad bought the car for my mom and surprised her with it when he picked her and me up from the base hospital after I was born. It was the first car I ever rode in, and on that first ride he rear-ended a military police truck while showing off the cassette deck to my mom. So not just the first car I ever rode in, but the first car I was ever in an accident in!)”
The car was later brought back to the States, daily driven for 13 years, and then stashed in a barn for about a decade when the turbo gave up the ghost. And if you know anything about old diesels — they’re slow at 100%. At half health? You might as well walk.
So off it went to Roush. And what came back is something truly special.
Funnily enough, in the original Reddit comment, u/captainklaus ends it with: “Hope y’all like it.” And to that, it simply is left to say: Yes, we all do. Very much indeed.
