Probably not worth as much as this one you bought and sold.
http://forums.pelicanparts.com/porsche-marketplace-discussion/856954-flippers-pissed-me-off.html
You gonna rebuild the engine? You gonna rebuild the gearbox? Is the suspension and brakes going to be better done than the last one? You deserve some value added if you bought someone's project to finish, but since you haven't given much detail on the standard it's hard to say end value.
Though as has been alluded to, if you leave the glass flares on the car and don't redo them steel it's a ding to the big picture perception of the standard. Is the motivation to leave them that the car is already painted? Might be worth it to paint the rear third again after the flares are steel, wide or original depends on the front fenders.