Where can I get a appraisal for insurance reasons?

I guess that is OK if you both agree that the book value is what your vehicle is worth at the time of loss. And if your agreement is tied to current "book" value that can change as well over time. For a fully-restored and mechanically upgraded vehicle, I doubt that the book value is even close to a replacement value. JM2¢.

Also Grundy is not a general insurance company. They specialize in antique and collector cars.

Grant