Legal Question in Personal Injury in California

You're right. That the boy had your son's permission to drive the truck does not mean he had permission to wreck it. He is liable for your losses to the extent that he caused them. His parents are financially responsible for harm he causes, at least up to a point.

Bear in mind that the appropriate amount to sue for is the entire loss, not just the amount your insurance didn't cover. The insurer will then be entitled to reimbursement. If you sue for only a portion of the loss, the insurer might claim some or all of it from you.

If the boy's family can afford to pay, your insurance company might be willing to sue them on your behalf. Such a lawsuit would seek to recover both the insurer's payment and the excess amount of your loss. You should discuss this with your insurer before you take any action on your own.

Good luck.

You are only entitled to recover the reasonable value of the totaled vehicle. You are not entitled to an upgrade.

If your insurance company deemed your vehicle a total and it paid you the full reasonable value for your vehicle, you would not be entitled to recover for an upgrade. In that case, your insurance carrier would be entitled to subrogate against the liable third parties for the amount that they paid out to settle your insurance claim.