Just to add a little interest to the conversation, this is an Australian brochure page from a Sydney based dealer. The relevant point is in the transmission section, last mentioned item in this section, where it says 'Final drive ratio'.
Remember that this brochure covers four door sedans, coupe's & five door wagons.
With so many B10 dif's [alloy with 4.11 to 1 ratio] showing up in 1200 wagons, then maybee it's true that they were being fitted by the state distributors, or even at dealer level, but whatever the reason, it would seem that they were not fitted at the factory, as the production 4.11 to 1 diff at this time used an iron carrier.
With the extra weight of the wagon body, & its intended load carrying ability, the lower ratio seems like a bloody good idea.
The standard ratio for the VB10 diff was 4.375 to 1, however a 4.625 is listed as an option. All had an alloy carrier.