For my 08 GT500 I'm paying a little over $700/yr. with Bel-air. It actually turns out to be about half that, since I store the car for winters and only need fire/theft left on the policy.
I have it classified as pleasure use, but have driven it in the summer to work a couple times. The downside of using Bel-Air is that they won't provide the 19A waiver (appraised value coverage) like Haggerty, Echelon and some others do....which means if the car ever gets written off, I'm not going to get anywhere near what it could be sold for. So a bit of gamble to be sure.
in 2.5 years, I'll be able to get the classic car coverage/19A waiver thru Zehr...which I think I'll do.