Ok, old thread but an update...
All V8 Commodores and the 5 litre competition bred LX & UC Torana ran the large 190mm type Salisbury rear axle.
The 4 & 6 cyl UC Torana as well as VB to early VK Commodore 4 & 6 cyl cars ran the small 178mm Holden Salisbury rear end with 25 spline axles.
The TD-TG Gemini petrol engines cars ran the same 178mm Salisbury centre except the axle gears have 23 spline machining where all other cars had 25 spline axle gears.
Later model VK and all VL ran the Borg Warner BW78 rear axle.
The TX and TC Gemini also ran a Borg Warner rear axle but it is NOT the same as the above mentioned Commodore Borg Warner. It uses the BW68 rear axle, same as is used in many 4 cylinder cars. I wrote about it
here.
Now the TX-TC BW68 diff is reasonably tough and a much easier axle to get a range of parts for as in LSD and ratio changes BUT, you still have the issue of a torque tube in a Gemini. You could adapt a different method of mounting the drive shaft from the diff nose so you still have the torque tube at the same time as keeping a gear set complete should you wish to change the 3.899:1 to a 4.1:1 and 4.3:1 out of 120Y, 200B, Corolla, Corona, Cortina to name a few using the BW68.
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