Some insurance companies will insure for additional value. Farmers allows up to $10k in additional coverage on top of book value, at least where I'm at. I had more than $10k in receipts for parts either bought online, from people on paypal, or Japperformanceparts. If you need more than the coverage they'll allow, you'll need to get an appraisal of the vehicle to present to insurance or use Hagerty or something similar. It wouldn't take much to total out a mirage or impreza L or RS lol