I think most of the vert parts are available now. The top and rubber weather strips are easy to find. The parade boot (top cover) is available. The hydraulic top pump is available, although mine is original and still working fine. The chrome hockey sticks that go around the edge of the top and rear body are available now too for around $400. So I would not be concerned about finding vert parts.Pros: performance parts for 302 windsors are plentiful and cheap. 'Verts are cool.
Cons: Convertiblet parts are expensive and hard to find? I think that's true anyway, I've never shopped for 'vert parts. Also, if this is a concours project then a 3 speed isn't the best for highway cruising.