Hey man I found a forum about diff ratios. I was wondering where you got your 3.9 ratio diff for your commodore as I've only found a 3.7 out of stock. I know its a long shot since its been about 9 years but its worth a try. Here's the link to the forum https://forums.justcommodores.com.au/threads/diff-gears-3-7s-or-3-9s.187974/