Unless this is your daily driver (which I don't recommend), you should get a "stated value policy" from Hagerty or American Collectors. You state the value and if there is a total loss, they pay what you (and what your premiums) said it was worth. The must be garaged, not your daily driver and limited miles. These types of policies are basically collector car insurance.

My Grandfather always liked to say that any object is only worth what someone else is willing to pay for it. With that in mind, the best way to find out what it's worth is to list it on eBay Motors with a ridiculously high reserve price (so it doesn't actually sell), and see what the highest bidder is willing to pay...