I saw a '69 this past weekend in a parking lot. It had a sheet metal insert where the wiper door used to be. The wiper arms extended through it and sat in recesses, i.e. it converted the system into an external one, with no moving wiper door.

i have seen a 71 that had the door removed and the guy told me he had gotten a hood from a different year after they stopped putting them in. don't remember what the actual year hood it was but i am almost positive he said he had to do a little modification to it. 

73 and newer hoods bolt on, and cover the wipers with no problems.  They come in most of the same shapes as the 69 hoods.    Corvette Specialties can help you.  www.corvettespecialties.com