This Mazda RX-8 is being built by Hepp Garage Racing Factory in Limanowa, Poland. The car was previously powered by a twin-charged stroked 2.9 L BMW M50 inline-six featuring a BorgWarner S300SXE turbocharger and Eaton M62 supercharger. They recently swapped to a twin-turbo 5.0 L Mercedes M113 V8 featuring two JRspec GTX3076R turbochargers and a 1 mm decompression plate. The V8 is mated to a ZP six-speed (BMW M57) manual transmission using a Poweride adapter plate, flywheel, and twin-disc clutch.
Photos of the previous engine setup.
Source: Hepp Garage Racing Factory FB page via Piotr