There was no
factory option roof rack for the S30-series Z range.
A USA-based company called AMCO made all sort of accessories for imported cars, and some of these were sold by Nissan dealers in the north American market (sometimes repackaged in 'Datsun' boxes), but they were not designed or manufactured by Nissan themselves - so not 'factory' in the true sense of the word.
View attachment 33447
Edited to add: NOT recommended. This type mounted onto the roof rail garnishes with clamp type fittings, which made a right mess of the stainless garnish mouldings. You can always tell a car which had one of these AMCO racks fitted in the past.