Well, if you're not using Iman (think of Iman just like you would think of Intralink, just a little more powerful) to interface with your car guys, then the revision rules would mostly be for your company. If, however, you are required to be on Iman so that you will get the latest information about the parts you have described, then the revision rules will not apply. I know that GM can be pretty particular when it comes to CAD standards, so I would think just as long as you saved a part for them in their naming conventions, it would fit into their Iman system.
When you say that 'Most times they have no clue' are you talking about the GM guys have no clue about what revisions your parts are at, or are you saying that GM changes parts and you have no clue that parts have changed?
Steve C