This Mercedes W126 sedan was built by W126 Iwangrosny in Poland. They replaced the blown factory motor with a 4.0 L BMW M60B40 V8 with custom headers and stainless steel exhaust. The engine features individual throttle bodies from a BMW S65B40 V8 and a Ecumaster EMU Black ECU. Behind the motor sits a S5D 310Z five-speed manual transmission with a PMC Motorsport adapter plate and lightweight flywheel, custom driveshaft, and factory W126 rear end.
Source: W126 Iwangrosny FB page via PMC Motorsport FB page