[Dean]

Just to clarify. On insurance. Unless you tell them and get them to give you a fixed value policy or effectively pay for a STI policy or possibly more, they will only ever pay you off on the older car's value. And, unless you tell them you significantly increased the HP of the car, you might get in trouble if you make a claim and they find out. Do you really want to risk not being covered in the event of an major accident wit injuries, and/or possibly being charged with insurance fraud to boot? Not saying it will happen, but it might.

Some might not even want to ensure a swapped car.

On registration, you just never know with SMOG checks/inspections what they are going to do. I doubt you could get a swapped car registered in CA, but you might.