Hi ian without an AC, meet Robert with a GD.
OK, on to business. Have a look in the articles section on this site, and look at decisions decisions. It will give you a very broad overview on choosing a cobra.
Its really a question of what you want, do you want an authentic replica, or a car that handles properly, what budget do you have, as you can build a good Crendon, DAX or Gardner Douglas for about 16K.
Also visit the local regional meet, details are on the site, talk to other owners and find out how many problems there have been with the build.
Visit the manufacturers, but don't get carried away with all those shiny bits, get a ride in the demonstrator.
They might all look the same, but some are worlds apart in terms of build quality, handling, etct etc.
Happy Hunting
Robert
