You have come to the right site. There are many people here who have a wealth of information on Cobras and more. Read through the BACC Forum and you will see that we meet in Livermore every Saturday morning and in Mt. View the first and third Saturday for breakfast. You will meet some great people and be able to see and learn about Cobras of every size, shape and color. You will also meet our Presidents. Which is all of us.
Be sure to check out Cobra Country. You will see many interesting Cobras for sale. Do purchase Curt Scott's "The Complete Guide to Cobra Replicas, Fourth Edition." It is full of information you *need* before purchasing one of these snakes.
Just my opinion, but I would hold off doing anything on Ebay until you do the above and have much more knowledge about these machines. For $40K, I would think you could find a small block (probably 351W) used, but not abused, Cobra. Do some looking through some of the other forums and you will learn a little about what some of us think is important. For me, that would include workmanship, balance and something *close* to the originals. And and since you are a local guy, a California licensed SB-100 car would be important. Check out one of those threads and you will see what I mean. Good luck, and I'll probabaly see you at breakfast sometime.
Rich