Car Parts Value..???
JMO, you are going to be stuck with getting what you paid for the item. The insurance is to cover loss of value to contents, not replacement $ value.
This isn't car insurance.
Have the seller send you an invoice or bill of sale. Hand write it with date and method of payment/total/paypal email account, scan it and send it to FE. That is proof along with your F&F payment
I know UPS is self insured up to a certain number, FE may be the same. FE used to pay out quickly. If it goes over a number they will send out an investigator to check out things sometimes. Last time I had a big $ item killed by FE I settled on the masx which was about $750 and sold the remaining broken up stuff to cover the loss. PIA.
You have to stay after them and escalate the claim at every push back. An FE authorized agent packaged it, that is a nail in the coffin for any denial of claim. Their own agent, didn't pack it properly. If all else fails, small claims court.