Get the car appraised by a recognized, professional appraiser. Yeah, I know some people think appraisals are not worth the paper they're printed on, but when it comes to insurance purposes, they are worth the money spent.
Two points to follow up Patrick's comments: First. When you get an appraisal done, turn it in to the broker you're dealing with. You might even want to have some sort of written acknowledgement from the broker that he's received it. The appraisal does you far less good if you wait until something happens to the car before you give it to the insurance people. I've seen several instances in the last 35 years where people did not submit the report and suffered the consequences.
Two. Use the value in the appraisal for the "agreed value" endorsement you add to the policy covering the car. Endorsements are like options for an insurance policy. With agreed value, in the event of a total (or even major) loss, the insurance company has agreed that's what you'll be paid for the car (less whatever deductible you may have signed up for).
Normally when talking value and talking `not new' cars, some companies have an endorsement called "Limitation of Amount", or some such. It basically says, that the insurance company will pay the value listed on the endorsement OR CASH VALUE, WHICHEVER IS LESS. Think of cash value as the amount you'd get for your car if you had to sell it by Monday, no matter what. Also believe that the insurance adjuster (a guy/gal you've never seen or met before) has an absolute encyclopedia of excuses to devalue your car. I've heard plenty of car owners tell me "My broker is a friend/relative/neighbour that I've known for XXX years, he won't steer me wrong", and suffered mightily for it. In most jurisdictions (and there are exceptions) brokers are prevented, by law, from settling a claim. You'll be dealing with this adjuster guy/gal you've never met before who's there to represent the insurance company. And their goal is to spend as little of the company's money as possible.
Bottom line: Make sure you have an agreed value endorsement on your policy. Most companies will ask for an appraisal to determine the value. Also. There are many ways to value a car. Market value - what you'd reasonably expect to get for the car if you choose to sell it. Replacement cost - the amount of money required to get you a car as similar as is possible to find, putting it in your driveway, licensed and ready for the road.
