So this one is pretty close...
It is built from a DB Class V36 prototype that utilizes dual Inline 6 Cylinder Diesels and Hydraulic Transmission which would be very similar to the RDC drivetrain and operation.
Horns and bells have been updated to North American prototypes.
Default horn is the Leslie A200 found one many as-delivered prototypes.
Default horn is the Nathan P3 believed to be appropriate for the SP prototype