What I was getting at was if the HQ's use the same HQ tailshaft between 6 and 8's for the same trans then most likely early commodores would be able to use the same commodore tailshaft between 6 and 8's with the same trans.
Im planning to run a 9inch and a 3inch thick wall single piece tailshaft after i get it running under its own power.It's only a cruiser so the stock diff will do for now.