Yes, Wordpress is pretty easy to skin, all you'd have to do is take the vBulletin variables from the templates and replace them with the absolute paths to vBulletin.
It won't automatically update when you update your header code in vBulletin, but its just as easy to do it in wordpress as well.
Ex:
http://www.brokensnooze.com/ (wordpress)
http://www.brokensnooze.com/forums (forums)