To run a 260, yes, there are more freedoms with the induction, but, you must retain the original carburretors.
With a 280Z, being injected, there are minor freedoms, to the internals of the induction system, but you must retain original intake manifold and rest of induction ( throttle body and airflow meter), same applies to any injected engine for GpS
It is not easy, or cheap, to get the Nissan setup to run better. The intake manifold is a crap airflow design at anything above 6000 rpm, but due to bigger bore size, the single butterfly throttle body can be made to flow very good cfm rates, with only minor work, same as what the front running Porsches have done.
Read the rule book, not just the specs sheets,,,,,,,
Have a look at the induction setup on James Flett's car, yes, it is Gp S compliant, and it works, but, that is just one part of a mechanical package, that works well.