I sometimes buy on ebay from the mustangs parts houses. Laurelmountain, for instance,is selling the 68 interior kit for a coupe for 609 instead of the 699 you have listed. This includes a Ford tooling dash (which I think is important.) I bought fenders from them on ebay before and things went smoothly. I actually pieced my interior together since I wanted custom single color seat covers in 66 Blue, which is also an option for you.

http://cgi.ebay.com/ebaymotors/1968-...em140217029665

One thing you might need that the kits do not have is the seat cushions or buns. At the least you will need some 1/2" foam from an upholstery shop to build up the seat cushions if they are flattened out. (And a set of hog ring pliers and couple hundred hog rings.)