There is another insurance thread, so I copied my reply from it.
About using conventional companies:
I can only attest to my experience. Others have different stories. I am insured with State Farm and I had a GN stolen a couple years back. When I first got it insured I made damn sure they knew it was not a regular Regal and after they ran the VIN, it came back as a GN and they had the value listed correctly or there-abouts. When I reported it stolen, I had to wait 30 days to see if it would be recovered. It wasn't and I contacted them again on day 31. The first lady I spoke with attempted to shaft me by saying it was 'just' a Regal. I politely informed her she didn't have a clue what she was talking about. She said if I had any other documentation to show the value to submit it and they would review it. I printed out the NADA/Kelley prices, about a dozen Autotrader ads, multiple pictures including the first place trophy I won at the World of Wheels in Shreveport, and the piez de resistance....an appraisal for about quadruple the amount I was first offered. I faxed it to them and the next day I was contacted by someone over her and he could not apologize enough for the first offer. He said after looking at everything he had zero problem with the appraisal price.
One thing you may have a problem with in using a conventional insurance place now is the NADA/Kelly books don't go back to 1987. NADA has a collectors book, I believe that now has the 87 T's and GN's. Just make sure they show you how they establish what they will pay on a total claim. Get an appraisal done by a certified appraiser to show the value and make sure they are close enough for comfort.
Most folks on here use the collector insurance places which is fine if it suits your needs. You agree on a value and you get that amount on a covered claim. For me the stipulations didn't work (can't drive it to work being the main one) so I went with a conventional company.
Sorry for the lengthy response, but the main thing I can advise, no matter which way you decide, is get an appraisal done by a certified appraiser BEFORE you need it.