Welcome to the madness. You may want to look at a few different sites with Cobras for sale. This site has a for sale section,
http://cobracountry.com Cobra country is a site just for selling Cobras and
http://ffcobra.com is a site for Factory Five replicas, which includes a section of cars for sale.
Depending on what make the car is, there are quite a few sites dedicated to the different manufacturers. If you determine the builder, chances are that there will be some local Cobra owners in your area that you can contact through the site. Typically Cobra owners are willing to help out.
You say the car has a 350 in it, I think that most will agree that a Chevy engine in a Cobra will lower the value of the car compared to if it had a Ford in it. Nothing wrong with the Chevy, but Cobras are a different market than street rods where a Chevy in a Ford is ok.
Good luck and the more info you provide the more input you will recieve from everyone on this site.