My insurance company, USAA, told me to document all my expenses so that they can properly value the car. They didn't want me to just get blue book for a car that is worth a whole lot more. They had no problem at all with the fact that I put in a 351 instead of the 302. The guy even talked to me at length about it.
Too bad they aren't open to the public.
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351W 89 Mustang GT Convertible