First, pick up a copy of the complete guide to Cobras & replicas. Not sure what the current edition is, but go to
www.cobracountry.com. You can purchase a copy through them.
Second, find out when and where your local Cobra enthusiasts meet. Drop in, and check out some cars. That's how I fell in love with the ERA 289 FIA.
Your post here will undoubtedly generate quite a few recommendations--all slightly biased. My own bias is for ERA, but I like Kirkham, SPF, Backdraft et cetera as well. It all comes down to how much you want to spend, and what kind of features you want (IRS, "genuine" vs. "replica", absolutely correct to the original body shape, et cetera.)
Check out some cars, ride in a few, meet some owners, hear their tales. Have a good time. Then, after you've done some research, pick your manufacturer and have a blast.
I've never heard of anyone being unhappy that they purchased an ERA Cobra.
Cheers,
DD