Sorry to question everyones intelligence hear but everyone keeps saying they owe you the cost of a car plus $25-35K in mods. Sorry but I dont think thats gonna happen unless you had the extra mods values specifically added to your insurance policy. Even if the dealer or body shops insurance has to pay you for the car they still only owe you for the way YOU have the car insured and since its never been said I am assuming you just had the car insured like any other stock 04 viper. Hence the insurance is only gonna cut a check for the value of a stock 04 Viper plus taxes. And another thing to insurance will call there dealer network they use to value the car, they do not go to KBB or NADA for values(and even though I hate insurance with all my heart this will benefit them in this case because the actual market on 04 vipers is nowhere near $55k). But of course you can fight and usually win these cases after 2-4 years in court(already been through this, and yes I won the extra $3k after 3 years of fighting in court, insurance will appeal as many times as the system will allow).
But if you dont believe me call your agent and ask him if you bolt on a set of $10k custom wheels/tires and your factory set is worth say $6k but you just leave your insurance as is and do not add the added value for the custom wheels/tires to the policy. Then lets say you go to the movies only to come out and find your 10k custom wheels/tires have been jacked. How much do you think insurance is going to pay you for the missing wheels/tires????? I can assure you it will not be $10k. Yes the insurance company has to make you "whole" again but they can only pay out on what you are paying for and that is for a stock car with stock $6k wheels/tires and even then you will be lucky if they dont try and buy you used stock wheels/tires since thats what they would classify yours as.
And last the OP's car being repaired will not brand the title as "salvage" or "rebuilt" the title will still be as clean as the day he bought it. But yes I agree there will still be a dimishied value and if the car is repaired you should get diminished value especially since you were not at fault for the accident.
I have learned all these things the hard way over the years by dealing with the scaming jerks and I am just passing along info on the way things work in the insurance world. Man I hope everything works out for you in the end. I have always had the worst luck with these crooks but always got paid what I thought was fair in the end but often wondered if it was even worth the time and stress for the extra money thats how the jerks work they wear you down until you will just accept the settlement. Best of Luck bud