Normally most 6 cyl holden 6's were fitted with a 3.36 ratio diff. Most 4 cyl's (mainly the torana's) had the 3.55 ratios.
Special cars such as the v8's and the gtr's and the like,  were fitted with the 3.08 and auto's were fitted with the 3.08 and the 2.78 ratio diff heads.