Here's the long and short of it. If you are in the business of selling classic and collector cars and you sell a car that you represent as "numbers matching engine" and it has been restamped, whether your restamped it or it was like that when you got it, and the end buyer can get an "expert" to say that the engine was a restamp, you CAN be hailed into court under a civil action. It does not matter if the seller is in one state and the buyer is in another. Now ultimately, the plaintiff may win and he may not, it all depends on the judge and/or jury and the particulars of the law in the jurisdiciton and how convincing a lawyer is, and how the judge feels that day, and the alignment of the planets, etc and so forth. But, if the buyer and his/her lawyer is motivated, than a lawsuit will be initiated. THIS IS FACT. In the end, regardless of who prevails, parties are going to pay legal fees and the lawyers on both sides win. It's how the system is setup.