Agreed Value Insurance

I have an Agreed Value Insurance policy on my 1979 LP400S Countach. The policy is with American Collectors Insurance. I have tried several times to raised the agreed value, but they refuse as their sources claim these cars are worth far less than I think.

Today I went to the "2010 Collector Car Price Guide" and found a listing for an 1978-79 LP400S in "excellent condition, maximum professional standards." So, this might not be up to totally Pebble Beach standards, but a very, very nice car in all respects. They list this at $77,500. In my strong opinion, this is SERIOUSLY low!

I suspect that a Series 1, LP400S in virtually perfect condition might go for 3 times this amount ($232,500) and this might sell in a few days or a couple of weeks.

So, I am asking what other people do to get their Countaches fully covered under an Agreed Value policy? What sources are used to establish value?

The agent I spoke with said they would consider evidence I could bring to the table. However, it must be convincing I imagine.

[I should point out that my car is not in virtually perfect condition -- rather, I think it is an excellent driver and very original with the LP400 motor and Bravo wheels, etc. I use the "perfect car" example above just for illustration.]

Thanks for any advice you can offer; I think this is not an isolated example -- rather a general problem we face.

Anderson