Hope you have made your decision , but to be honest either one will be an awsome choice for you and both have great resale values.
Its worth mentioning that Shelby himself had purchased bodies and chassis for his continuation cars from Kirkham as well for a while. SO in actuallity some preowned Shelby continuation cars could actually be a Kirkham in disguise perhaps. Its interesting. Check out the below link
http://en.wikipedia.org/wiki/AC_Cobra