As Alan has covered before on many occasions, the dealer option topic often gets very messy and suffers blurred market distinctions based on the very US-centric dialog that dominates the internet about these cars.
The one country that had a genuine, advanced, official option range was Japan - one that mirrored the variants available there on the cars (e.g. at one point there were 7 distinct models available there - Fairlady Z, Fairlady 240Z-L, 240ZG, etc., etc., - compared to the one available here, or the [very different] one available in the US etc.).
In the US, the kind of things you see added on these cars in period, possibly from new, such as slot mags, side protection trim strips, bumper accessories, etc., were aftermarket pieces that dealers sold. For example, see the Amco ad below with pics of some of the add-ons they offered that often turn up on US cars. I've seen a few of these bits on imports.
As for the UK, Zs were no different from many other in-period classics that experienced a swap to Wolfrace slot mags as an aftermarket thing. Same with Webasto sunroofs or the occasional vinyl roof, etc. But all that stuff was not something specified by Nissan.
red baron on this forum worked for a UK Datsun dealer in period and used to work on these cars as they arrived to them from the manufacturer. I've had a couple of interesting conversations with him about how they came packaged and what they came with.
