Help with Insuring my Son's '68 Dart

We need help finding an insurance company that will insure my son's '68 Dart for its appraised value ($19,500). State Farm (our current company) will only insure the car for "fair market value", which of course means we'll get basically nothing if its stolen or wrecked. To insure it for the appraised value, they have to classify it as a "classic" and then we can't drive it more than 2000 miles per year. I have gotten a quote from Grundy, but they are prohibitively expensive for the other 2 vehicles we have to bring over to get them to cover the Dart (more than 2x State Farm's rates). The Dart is a daily driver (6000 +/- miles a year) and is not garaged.

Does anyone have any suggestions..?? I don't see why an insurer wouldn't just quote a price based on the appraisal, but apparently that's just trying to use common sense......

Thanks in advance.