I always laugh at Shelbys Glove box signing...My brother sent his GT-350 mustang clones glovebox door to Ol' Carrol Shelny back in 2006, along with his $60 fee to have it signed, came back with a signature and certificate of authenticty that he signed it also, had nothing to do with correctness he never saw the car, I guess its kinda hard to mail the hood!
Carrol Shelby pimped his signature for whoever had a extra buck, gave the money to charity he said.
Do your homework well on this one, its a common repoped car, like my '32 roadster, only worth as much as all the others that show up at the cruise night that look just like it just a different color combo, cool cars for sure, probably not bad on price if your going to build one but not a steal either, Almost all have a 427 in them or a 289 and done very close to original. Have fun but don't fall to hard for that signature!