Written appraisal would be a great plan, for the serious buyers it adds credibility to your asking price, and should help keep the low-ballers and tire kickers away, too! Market is weird on cars now, the really first rate pieces fetch some big bucks, the other stuff just isn't doing as well... The more history of the car and documentation you have concerning the car and the build, the better off you'll be for resale, too! I always put together a photo album of before, during, and after the build, with email, it's really easy to fire off a copy of it to potential buyers.