Thanks Alan , UK market is the same as the Australian market , I also checked the parts catalog for HLS30 except USA and Canada . The book says yes, the FS5C71B has the same part numbers for the gears starting from 2.906 .
In Japan, the gear ratio was discontinued after September 1973. Never applied to S30 models again.
I would say the ratio is not rare, it is rare only in Japan, after seeing Gavin and Alan posted above.
I am also huge fan of FS5C71A , first of all,
It has a look , things of beauty. I can spend hours just looking at the gear box.
Japanese people tend to give up rebuilding the FS5C71A because they think no parts available , they do not know there are some nice parts vender in the US.
However, Mr.Kawashima who did wonderful work for my two FS5C71A now became famous among not only S30 community, also GTR and SP/SR .
Mr. Kawashima recently started to service for R192 diff , he managed sourcing some NLA shims and bearings from manufacturers in Japan. He even also made special tools for disassemble and assemble.
https://www.vintagecraft-e-za.com/s30zのページ/日産旧車の駆動系レストア/r192デフ-その2/
Kats