As said above, looks like 68, vin tag is stamped on the left front on top of the inner fender (no removable tag), if there is a tag you can check it on the shelby registry. There should be a tag on the driver door that list all the options, link below will help decode. If it's a shelby it's worth a pretty penny restored or not, if it's not real it's still worth good money, could be finished as a clone or bullitt.
The rear frame rails, front floors and cowl are the first to rust on these.
Hope this helps.
Mike
http://www.mustangdecoder.com/plates.html#1965
http://www.teamshelby.com/forums/
http://forums.vintage-mustang.com/