i do not know if they are the same blocks, but here is an article. jim
http://www.enginebuildermag.com/Article/105776/brand_new_vintage_409_block.aspx
stole the link from the corvetteforum.
http://www.enginebuildermag.com/Article/105776/brand_new_vintage_409_block.aspx
stole the link from the corvetteforum.