This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
What other queries do you do against these tables? Because i do not see any reason of having separate ids for every car number.
Regarding delete and re-insert. You can try to add a columnt last, and do a simple update of records setting for new records last to 1 and for old to 0. If you have more records, then you had, then switch to insert mode. I do not see benefits of this approach, however it works in some of my systems.