Chances are, no matter what you did to it anyways, insurance just doesn't give a damn. Your best bet is to strip down the stuff you put into it, and let them value it that way. That stuff isn't going to budge them on value anyways. If the book says "this", you will probably get "this". **I do not think replacement cost works on vehicles that are no longer manufactured, so they will have to go by value.** I had a friend go through something similar with an older Honda CRX and that was how it was played out for him (his was stolen and left for dead too
). It is too hard to comp a vehicle that yuo simply, do not see anymore, heh.
Just keep in mind, and be up front, that when they value it at "book value", you are stripping off the things you did to it. I was up front with Allstate years ago on a vehicle that was totaled and I told them if they didn't cover the bells and whistles I put into it, I was taking them out. They really did not give a hoot, but again, I was up front about it. After the fact, you are probably going to lose that battle.
Good luck. Dealing with ANY insurance is cancer....
Gary Noonan
'01 S/C VX / '18 Forester XT