Are there any books concerning the wiring of a Z then? Or could I possibly get by with threading the ZX harness directly next to the 260Z's harness?

It is not just the harness you need. It's the computer, and all the support items that are necessary for the system to function, and no you will REPLACE the old harness. The gas tank and fuel pump are different among many other things. By the way I see you live in California. Does this car need to pass emissions testing?

It doesn't have to pass smog any longer. I have the ECU and the AFM as well. Oh, and the intake manifold. I know that almost all of the ancillary parts have to be replaced (alternator, starter, rotor... that's all I can think of but I know there's more).