The D within the engine code stands for dual overhead camshaft (DOHC). This really is attained by fitting an RB25DE or RB26DETT cylinder head and or turbo to a standard RB30E/T block. The RB25DET will not be typically used. In 1995, Nissan revamped the RB25 collection and designed various variations. https://emilioiomjb.blogozz.com/27861496/the-5-second-trick-for-rb26dett-engines-for-sale