Tampering with the vehicle identification is a felony in my home state. I see more trucks titled off the engine number than off the door plate, and at least half the engine numbered trucks no longer have the motor to match the number.
The process to change the number isn't difficult in Washington if you have a title that matches the motor, and the motor is still in the truck. I've not yet tried it without a motor, though one of my most recent purchases is in fact an example of that.
Some people think I'm too picky, but for the most part I will no longer purchase a vehicle with out a clean title that matches the serial number or VIN on it. Even with no title there is a process that will solve the problem, but it can take years, and some vacation days, and moving it around on a trailer, to make it all happen.