Haggerty, Grundy are 2 of the specialty car insurers that come to mind, but they both have rules about your OTHER vehicles and household drivers.
Other vehicles can't be older than a certain year (even though they are insured with ANOTHER company)which pissed me off because my POS daily driver and my sons car were older than their "minimum". Their rocket science theory was that if one of the POS's broke down, I, or someone in the household, would use the Viper to go to the store, drive in the snow to get a quart of milk etc......yeah right!
The benefit of these specialty insurers is that you can set a specified agreed value coverage for the value of your vehicle that you come up with (and you will pay accordingly).
So I just stuck with the carrier that insures my other vehicles and my homeowners (going on 15yrs now), Nationwide, for which I pay $600 additional for the Viper with no BS rules and regulations. Haggerty wanted $500, so for $100 more per year I don't have to worry about their bozo rules and regulations and 50 question questionaire that asks what you eat for lunch and what sports you watch on TV.