The D from the engine code means dual overhead camshaft (DOHC). That is accomplished by fitting an RB25DE or RB26DETT cylinder head and or turbo to a normal RB30E/T block. The RB25DET is not really commonly used. Although it’s not as mentioned as a number of its cousins, Nissan’s RB25DET https://spencerpxktr.bleepblogs.com/28730756/rb26-engine-for-sale-can-be-fun-for-anyone