Call jonb or woodhouse. Find the highest prices you can and what they sold for. Dont bother with KBB as its a joke. List out your mods, if any, and have receipts for them. Im sure your policy is a "market value" like most, if so then your not gonna get alot, if its "agreed" then your good.
Once the insurance company tells you what they're going to give you for it, you can rebuttal but be cautious that they can retract there offer and then offer you less. I know a guy who tried to go back and forth with them and got 10k then what they originally were paying. Fact is viper prices are down and i just hope your friend gets a decent amount.
When mine got totalled, my agent let me remove my parts but she wrote the car up as still having those parts installed. Got paid for the parts by insurance company and sold them on here.
I had 7k JM heads and insurance was only giving 900 for them. I got the 900 from them but sold for 4500 on here (jesel rockers included).
Also they only wanted to give me 900 for my paxton, so i pulled that also and sold on here.
another word of advice, if your friend has mods, have him pull them off before your insurance guy looks at it, that way if anything gets damaged while removing the parts, you can just blame it on the accident and you still get paid for the parts.....this is advice straight from my insurance agent.