You may want to continue the process with Progressive. Their program is a good one. You may even be able to deal direct with them on their internet site & phone.
Make sure you have an agreed value
no matter who you go with. You can start with the purchase price. Send them a bill of sale & a couple of pictures. You can always increase the insured value, at any time, with documented expense reciepts and/or an appraisal. (Appraisal are tough sometimes ... to find a dealer that is qualified and will do that for you).
Indemnify yourself for what you've got in it, and increase it as you go along.
There are some previous discussions in the following:
With many underwriters ... you will have to be careful on what they will cover and what they exclude, with particular attention to the depreciation factors they apply to certain items.
Best bet, read the policy first. These are boiler plate although usually specific and exclusive to each individual insurance company. Your agent can get you one if they are appointed to sell their policies.