Need A-body V-8 radiator
if you want aluminum there are lots of different ones, but the
best there is come from Smith's Radiators. up in cambridge city, indiana
http://www.smithsradiator.com/contact/index.html
big money though.
if you just want a stock replacement radiator, most of the local napa's carquest autozone etc can get you one cheap, and you dont have to pay shipping.