I have State Farm insurance. In 2005, I extensively researched this subject and found that staying with State Farm was cheaper than going anywhere else. The only qualification they had was to get the car appraised.

I used Great Old Cars and State Farm accepted that appraisal and insured my vehicle at 100% of the appraisal value (10.5K at the time). Before that, they were saying my car was worth $4500. Clearly worth the $50 I paid to have it appraised. My premium went up slightly (maybe $5 a month).

I pay about $28/month for FULL replacement coverage.

Here's the webpage to Great Old Cars: http://www.greatoldcars.com/