As you likely know by now that is "beyond economic repair" and this has happened to me twice.
My first was my first Z that someone drove into for me, i simply delayed collection and ensured anything of value was either off the car or replaced with stock parts. I sent them some autotrader and ebay links showing cost of replacement and I got "replacement cost" rather than the "book price" like they like to give.
Again I had a GSXR-750 wrote off for me this year, I paid a low price in Jan being the winter but come summer when I looked to replace I did the same, they paid out 1,200 more than I paid for my one in Jan to cover the price rise come summer.
All this said the key is being honest with your insurance about mods, where it is kept, and your particulars etc....as you never know when bad stuff happens. If they have no reason to question you, in my experience, just push for what it would cost to replace like for like and accept no less and they will pay. If there is discrepancies...well you signed a contract and they are well within their right to tell you to do one.
I do feel for your loss though, its terrible to have to see this of something you have given so much time and effort for