This is indeed R4130. The "all custom" that Mr. Egbert references in his ad refers to the many hand-fabricated, non production items installed on the car by Studebaker Engineering that were unique to this car, which, as we know,was was a "test mule" car for running changes to be introduced on the '64 models. Most of these items were hand-made by Engineering, and were somewhat different than the items as they subsequently appeared on the '64 models. The "built by Granatelli" references the performance modifications that were done to 4130 by Granatelli after it served it had served its duty as the "prototype"-for the interior and exterior engineering testing- at that point, the car was sent to Granatelli's shop in Santa Monica, and an R3 engine was installed, along with a unique supercharger cooling unit, as well as a set of Halibrands. Many engine accessories were chromed as well. The "custom interior" undoubtedly references the non-production styled thick back bucket seats, pre-production tilt wheel, pre-production solid color interior, wood grain trim metal-grated interior air vents, ('64's had plastic grating) '64 style (but hand-made) rear window latches, door handles,etc etc. Quite probably as a "test mule", the finish of the car took its lumps, and George Barris's shop in Los Angeles was a logical choice for new paint.