What you are proposing is not new, but it does have its difficulties. Actually the only thing simpler than a Cobra chassis would be a "T" Bucket hot rod chassis - there is nothing to a Cobra chassis that would make it difficult to replicate.
However firstly you specified a DAX, it is monumentally unlikely that Dax (or any other manufacturer) will supply you with copies of chassis drawings which leaves you to design your own, or adapt an existing design. (PS if any of them do I would SERIOUSLY love a copy!)
There is an Australian company that has plans for a Cobra chassis approved here for use with 460 CI engines. A lot more complicated than it needs to be for a more "traditional" design, but if you want a starting point it is probably a good way to find out just how much you DON'T WANT TO DO THIS! See http://www.edds.com.au/cobra.html
. Definitely not a simple twin tube cobra frame.
If you decide to go ahead, two books you need more than you need a girlfriend/wife/partner are "Racing and Sports Car Chassis Design" by Costin and Phipps, and "Sports Car Bodywork" by B. W. Locke.
Let me know how you go, and if you need any more specific advice I am happy to be contacted. Might even take on drawing up a Cobra chassis for my own amusement.