I would go with Hagerty, they have been great to us.
The other collector car insurance companies were not even close in price and covering the upgrades, as well as the appraised value.
We paid around $100 to have the Z appraised and Hagerty honored that price. Hagerty understands how real car owners treat their cars (like their children).
FYI, I have no connection to Hagerty whatsoever, I jsut don't like to see my fellow car enthusiast waste time with standard car insurance when none of us are discussing standard cars.
Source:
Classic Car Insurance Companies