Will any sr20det engine fit in your Nissan 1991 240sx hatchbackmeaning a 1991-1998 sr?

Yes, any SR20DET engine from the 1991-1998 range can fit into a 1991 Nissan 240SX hatchback with the appropriate modifications. The installation typically requires an SR20DET-specific motor mount kit, along with compatibility adjustments for the transmission and wiring harness. Keep in mind that additional upgrades for cooling, fuel, and exhaust systems may also be necessary to ensure optimal performance and reliability.