Can a 2.8L diesel cummins fit in a Nissan d21 Its obviously going to need some extra work to fit but is it easily possible?

Yes, a 2.8L Cummins diesel engine can be fitted into a Nissan D21, but it will require significant modifications. You'll need to address issues like engine mounts, transmission compatibility, and possibly the cooling system. Additionally, modifications to the wiring harness and exhaust system may be necessary. While it's feasible, the complexity of the project can vary based on your mechanical skills and available resources.