I think a factory front bumper and rear reflector, CF interior pieces put back to stock would do a lot to help the sale without much out of pocket.
Not everybody is a purist and it looks like the car is solid, built to go and look like a maniac. I dig it.
It sounds like you're realistic with the 40-50% return comment.. If you're serious about selling list at 60-70% and see what happens.
Here's a data point for you on a similar (built to the tits grey turbo maniac) car:
http://forums.pelicanparts.com/porsche-cars-sale/820301-1976-turbo-911-professionally-built-lightweight-track-street.html