Thank you for your reply. Since there is a contract, the vendor has no right to breach it's terms. An agreement has been created and you can file a lawsuit against them for breach of contract if they fail to follow through with their side of the bargain.
Alternatively, you can see if they are willing to settle with you by giving you an upgraded (more expensive car) for the same price....if so, make sure they put this in another contract. If they are not willing to work with you, then you have the right to enforce the contract for its original terms.
Finally just to be safe, double check the sales contract and make sure there is no rescission clause ( a clause that would give either party a certain period of time to cancel the entire contract without any legal obligation), if there is such a clause make sure the time to cancel has expired or else they would be able to cancel the contract without any cause of action.
This is only legal/research information. Consult a local lawyer for specific legal advice. No Attorney Client relationship has been created. Don't Forget To Click ACCEPT.