You don't say if you are looking for an aluminum or fiberglass. I would recommend fiberglass if you are going to drive it at all. The alloy cars can be reasonably fragile with rock dings and hail will be a major problem.
Shelby still makes them. (Lots of people don't know this, I don't know if you do.) They are still the premium builds. Both fiberglass and aluminum. There is an aluminum Shelby CSX4xxx car for 160K that is probably the steal of the century. Glass cars are also will built. My Cobra was CSX4005LA and was one of 6 carbon fiber cars.
Kirkham makes a nice alloy car. Older Shelby CSX alloy cars were built in Vegas. Later they were sourced from Kirkham but unique in that there were no interchangeable parts. Now the alloy CSX cars are just a Kirkham, and I would be hard pressed to justify the price difference, except that Shelby's do appreciate and all the rest go down.
For glass cars like Superformance makes a really nice car and it is a finished roller. That is, as with Shelby CSX and Kirkham, it is a completely finished body that all you have to do is add an engine/transmission of your choice.
Other glass cars in my opinion are hit and miss. Factory Five does offer a finished roller, but the inside is not "original spec". They also have a kit you assemble and I've seen some perfect kits and some totally abhorrable units that I would personally be ashamed of.
As was mentioned above there are cars that are based on original style frames but also built on a donor Mustang. Stay away from those kits. ERA makes a really nice original style car but it's in the SPF league and I think SPF is better in recent years.
Look on
www.cobracountry.com for used Cobras. It's the clearinghouse for Cobras. It'll give you a good idea of the differences in specs and prices. If you would consider Shelby or Kirkham, I would encourage you to look at existing cars since the lead times for new builds from them are over a year (I heard Kirkham might be longer).
Good luck!!!
I loved my Cobra and may very well go back to one. (My wife hated it, wouldn't ride in it, so I sold it to get the GT). I would buy a CSX again (she won't go anywhere anyway) since they do so well on resale.