KOW-TUNE is a company in Przemysl, Poland specializing in Mercedes performance. One of their recent projects is a Mercedes W124 coupe which received a 5.4 L M113 V8. The AMG motor made 356 hp (261 kW) and 515 Nm (379 lb-ft) of torque. The V8 runs on a LC standalone ECU and features a 3-inch stainless steel exhaust and upgraded fuel system. KOW-TUNE may add a turbocharger in the future. Behind the motor is a NSG-510 six-speed manual transmission capable of 800+ Nm of torque. In the back of the car is a 210 mm differential from a W140 with a 2.87 ratio and E55 AMG axles.
Source: KOW-TUNE FB page