Just wanted to add my five cents in. I own a 1970 challenger convertible and over the years I've been restoring/upgrading parts on the car. Since 1999 I've seen prices for parts specific for convertibles go from $100 a peice to $450. I haven't bought parts in over a year since I'm waiting for my engine to finish being built but my experience is you always pay a premium for convertible parts.
The parts are move available now than previously. For instance windows for the whole car can now be bought but I think they are $750 - $950 now. The list of unique parts is pretty long and in the long run I think your better off buying a nice convertible that is finished. Especially now that the market is repressed. Cars are selling for $30k - $40k less than two years ago. The cars are not cheap but I suspect the prices will only increase in time. That is why the prices for parts for these cars haven't gone down as much as other Ebody parts.
