My dad restores old BMW's and he uses a collector car insurance company. The company sends a qualified appraiser that actually knows cars out to take note of parts that are rare/nonexistant/custom. He recognized quality of paint, if your engine is rebuilt/modified, suspension modifications, wheels, tires, stereo, etc. The car was appraised at 12,000 and he pays about $140 per year(yes I did say per year)
I'm about to do the same thing with my truck and I'll let you know how it goes.
Evan