http://forums.justcommodores.com.au/v6-development-modification/71234-diff-all-you-need-know.html
For those interested in other diff ratios for the BW78, the Nissan R31 Skyline and Pintara also used the BW78, these were fitted with 3.73 (manual and very rare) and 3.89 and 4.11:1 other ratio's also available are 3.27 (VP GTS). ford also used the BW78, i'm certain that the XD and XF falcons had the BW78 but not certain what ratio's were used. i've heard 3.23:1
VT series 2 onwards they fitted the BW80 diff, which has a larger crown wheel and pinion, and also different ratios. Parts from these are not interchangeable with the earlier BW78.
VT s1 BW 78, 4-spider center, 28spline axles, 3.08:1 open and LSD (same as VN-VS)
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Looks like you can use the centre from R31 Skyline, Pintara, XD-XF Falcon, 3.27 appears to be from a VP GTS and I'm not sure what else, probably hard to find if they were the only cars produced with them.