I plan to someday take an Older Frame like a 260Z or a 240Z older model, and put a 280ZX Turbo engine in it, I have done some research on it, and yes it will certianly be a BIG JOB. You will have to route all the wiring and find a place to mount the CPU, as well as run all the other wiring. It will be a big job, but worth it in the end.
I would read one of the repair manuals that covers all
the wiring of the Fuel Injection setup, and the sensors and so fourth so you can get a better idea.
There is no real need to remove the wires from the ZX engine simply unplug the computer harness at the computer and carefully pull the harness through the firewall into the engine bay, there is a grommet on the harness that will pop through the firewall then all the wiring will slip through. Coil the wiring on top of the engine and leave it alone. Remove the wires from the other sensors, ie oil pressure, temp, AFM, etc, but leave the fuel injection intact. The computer will mount in basically the same location in the 260Z. You may have to cut a hole in the firewall for the harness but one is likely there already. Basically this is a bolt in conversion that is very simple.
One thing to make sure of is good clean electrical connectors and you may have to change the fan shroud since the ZX uses a different fan than the 260, or even easier use an electric fan. Definetly try to keep the ZX around until the 260 is running and driving that way you will have all the parts just in case.
I have a 260 with a stroked 280 block and someday I want it to be fuel injected. Could you answer a couple of questions? First, what about the fuel system? Of course a 280 fuel pump and stronger fuel hoses will be required and maybe even the metal fuel lines would need to be replaced. What about the gas tank though? I have heard some people say that it should be replaced with a 280 tank because the return fuel is under higher pressure than if it were carbed. Second, and this may sound very simplistic, but how do you actually tie in the F.I. with the 260's electrical system? Can it handle the extra power requirements? The more questions I get answered, even if they seem simple, the less intimidating a task it becomes.