Everyone just calls me Bill,
These modifications would have been performed after it left Ford. When Shelby started building it's racers for Ford, they would order small quantities. They would do a complete tear down of the car, and rebuild it to FIA or SCCA standards at the time. Individual race teams could also order cars and send them to shelby on their own dime.
I can't say with 100% certainty that this car was a racer, but some of the present day indicators do point that way. What I mostly hear of is some past owner had a new set of tools and a garage, and the next thing you know, you have a shelby clone. I do think it would somwhat difficult to clone or fake a Group I or II racer though. There isn't really a lot of information available about them. Sure, if you were diligent enough you could find enough information to make some educated decisions, but there would still be many unknowns about how the cars originally left Shelby.
I still say the best thing would be to contact Shelby and get thier input. They would know original hole diameters and placement.
Edited by - FoMoCo Dearborn on 02/24/2011 09:17:58