Hello everyone I'm new to nicoclub and I have a question. So I bought a 1996 Nissan 300zx twin turbo back in November and as of last month the motor died. This 1996 model of the z had the Variable cam timing (NVTC) dropped and obd2 introduced. I'm going to be buying a 1990-1995 vg30dett imported from Japan that comes with all the accessories, wiring harness, and ECU. What I'm concerned about is will I have any issues hooking up the obd1 wiring harness and ECU to my z and can I still use the existing manual transmission? I'm also not worried about smog just want to know if I'm in the clear before I buy everything.

This has been covered in some detail so do a search on the forums.

In short though:
1. It is highly recommended to get a new EFI harness (whatever you get with the engine will be damaged and likely crumbling). You may have to re-pin the power connection (6 pin plug on EFI harness) to connect to your 96 body harness but the ECU plug will be plug and play.
2. The transmissions are all the same for all year TTs (except the 98+ which have stranger synchros but dimensionally are identical).
3. You will ABSOLUTELY lose OBD2 operation and if your state/county requires OBD2 operability to pass smog then you will have to source and install an emulator or a standalone which is a rabbit-hole all its own.

All that said be weary of JDM engines, best route would be to rebuild once you receive it or buy a built engine from IPP, Z1, SZ, etc.