To change the posts to have the userinfo on the left hand side, as was default in vBulletin 2, do the following:
AdminCP > vBulletin Options > Style & Language Settings > Use Legacy (Vertical) Postbit Template > YES
After changing this, any changes that you would previously have made to the postbit template should now be applied to the postbit_legacy template.
You'll also have to reapply any changes that you had previously applied to only the postbit template.
AdminCP > vBulletin Options > Style & Language Settings > Use Legacy (Vertical) Postbit Template > YES
After changing this, any changes that you would previously have made to the postbit template should now be applied to the postbit_legacy template.
You'll also have to reapply any changes that you had previously applied to only the postbit template.