Ohh, boy ... not 24 hours has gone by, and you unwittingly fire one right between the eyes, LOL. 😄
Let me start by saying this: we could devote an entire thread of many multiple pages of discussion to just this topic. And I'd venture to say that, in the end, we could only conclude that "No one knows for sure". I'll start off with some things that I understand to be true, and then I'll probably have to pass the baton for more input. In an attempt to provide a short summary:
Some things that I believe to be true: Nissan made 40 +/- Works Rally cars utilizing, for a lack of a better description, a PZR chassis (Nissan parts-manual-speak for "Z432-R" chassis). My best understanding is that, although Nissan continued to make Works rally cars for the 1972 season and beyond using the same PZR chassis forms, none of these later Works cars were "Lightweight Spec", due to the FIA rules changes for the 1972 season which prohibited thin-gauge panel use, and other lightweight materials, in construction.
Some things I just don't know for sure: Of those 40 +/- Works Rally cars, I GUESS is that at-most 20 were "Lightweight Spec". I get to this number by counting the known Works prototypes, known pre-1972 Rally cars, and adding one or two more phantom cars that perhaps no one (including me) knows about. I don't think there's a likelihood that there could be more than 20. If pressed, I'd say there's probably slightly fewer. This count of ~20 is IN ADDITION TO any Z432-Rs (which may or may not be lightweight- see below), which were production cars.
But wait, it gets more complicated. What does "Lightweight Spec" really mean? I'm using it in this case to describe a car that was produced, at least in-part, with SOME lightweight panels, and also with some combination of acrylic glass, along with fiberglass doors, hood, and hatch. The reality is more difficult to parse, because it's my understanding that each batch of Works Rally cars were built to a purpose. Even though within each batch of 3 to 4 cars the construction was probably roughly identical, cars built for other races possibly used different panel thicknesses on different parts of the car.
Other things I just don't know for sure: I just don't know exactly how many Z432-R's were "Lightweight-Spec" (using my definition above). Certainly several/many of them are. Were they ALL lightweight? This question is a grey area for me, as I've heard different stories. Did they continue making them lightweight after 1971? I'd venture to say they certainly could have, and would have reason to do so; adding to the "lightweight" complication is the fact that Nissan Works was also producing track cars at the time, which is a whole other tangent to the Works program that I know almost nothing about. Ergo, to potentially increase the running-total "Lightweight Spec" count, we'd have to consider the Works race cars in the mix.
Certainly more information, corrections, and thoughts to come on this topic.