I don't think there's any secret recipe to manufacture an alloy body, say like the Kirkham's version of it. Kirkham has posted several videos entitled "Kirkham Aluminum University" on YouTube and they also have 72 pages posted online on making the aluminum body:
http://www.kirkhammotorsports.com/book_aoe/aoe_18.pdf
But the OP's Cobra has no Kirkham VIN# and at a very minimum that radiator opening looks wrong, "camera angle" or not.