Hey Dan,
I know you state a convertible but a friend of mine right here in town a block away from me has this Coupe For Sale which is an Oshawa built SS with complete "Born With" Drive train. A nice project for you to put together.
He had it on eBay last week, here is the link for details.
http://www.ebay.com/itm/1969-Chevrol...p2047675.l2557
Good luck in your search if this does not interest you.