Pretty responsible persons and also the engine is running great following a few months of use. Very encouraged.The RB25DE cylinder head through the A31 Cefiro C33 Laurel or R32 Skyline (aka: Non VCT) is usually used. The RB25DET (through the R33 Skyline or C34 Laurel or Stagea) head can also be used, even so an external oil feed have to be fabricat