To create the car from Gone In 60 Seconds, Eleanor, start a Muscle Car Career mode. After you complete the first three territories (Kempton, Downtown, and Fortuna), a new territory will be unlocked. In this territory, win two races in the area to the far left (Silverton) to unlock the "67' Shelby GT 500". After you get the car for $108,000, return to your safe house and select "Customization". Then, choose "Aftermarket" and use the following customizations:

Aftermarket

Body Kits: Body Kit # 2
Wheels: American Racing Shelby Razor
Visuals

Paint: Candy Red section top row, last box to the right (silver)
Vinyls: Stock; edit color to black
Wheel Paint: Chrome, in the red section, seventh row down last color to the right
Window tint: Light black