Cheers guys.

A bit more digging and I spotted a 'tag' that was riveted to the underside at the front left.

OB2950023
M70 Ratio: 3.889
065 - 01798

It measures ~1295mm between the 4 bolt brake/wheel/hub mounts at each end.

I was looking to find a higher ratio diff (having manually deduced the 3.9 ratio). It's all mounted in my Lotus 7/Caterham type car and low end torque was a bit wanting.

Then I started building a spreadsheet of RPM/gear/speed and worked out that it's probably not worthwhile unless a 4.9 or something drops into my lap (not likely).

Bearing in mind this is all in South Africa, the BW68 apparently was also used on the Toyota Corolla (which has always been quite popular here), so it sounds feasible.

I might take a closer look at the local 1400 bakkie/ute, not sure what they're using here, though something tells me it'll also be 3.9.

It's all got to come out anyway to replace the suspension rose-joints, so I'll have some time to work out a plan.

Thanks