I'm not sure if Washington uses the engine ID as the VIN number or not. I would check with the local DMV, tell them you are planning on switching engines in the 1/2 ton truck, and ask them how it will need to be inspected/licensed.(most states want the vehicle to get inspected by the highway patrol to check for stolen vehicles) There is usually no problem switching the ID plate inside the door frame, which is what I would do. Then you just use the 1/2 ton title. Just my opinion - take it for what it's worth.
