Yamaha first consulted to Toyota way back on the 2000GT. They built the cylinder head and the wood inlays for the interior (they make a buncha pianos). The first three Supras have inline sixes derived from the 2000GT's M-series block (built in house), with GE-series heads by Yamaha. Yamaha still builds all of Toyota's GE-series heads, but at this point there aren't too many motors with GE-series heads. Yamaha also contracts out to Ford--they did the motors for the various Taurus SHO models and now the Volvo XC90 V8.