I did this modification in July 2014, it's now November 2015 and it's still running strong.
The modification is totally concealed in the TIU so the original harness is unchanged. To revert back to original is simple as changing the TIU.
The instruction is based on a 1977 280Z, but it can also be used for the 1978 280Z TIU with the terminal block connector. You will need to cut the metal strips that connect the terminals in the terminal block to the circuits. Be sure to leave enough to solder the wires. The terminal block can be fitted, using the original screws, to the aluminium base plates.
See link to the files area where you can download: