Rob - Just wanted to thank you for mentioning Hagerty's in what of your roundel pieces. I looked into it a year ago and it has been great. I am down to three BMWs but two: 85 M635 and 97 Z3 2.8 are with Hagerty's now.
There are a number of companies who offer insurance for classic cars, but I've always used Hagerty and have been very happy with them. Buying my Bavaria and insuring it for six grand, I think the annual change in my policy was $36.