Will a ls3 fit in a1984 -1989 300zx?

Yes, an LS3 engine can fit in a 1984-1989 Nissan 300ZX, but it requires significant modifications. This includes custom engine mounts, a compatible transmission, and adjustments to the exhaust and cooling systems. Additionally, modifications to the wiring harness and potentially the fuel system may be necessary. Overall, while the swap is feasible, it involves considerable effort and expertise.