a motor vehicle support group for mounting an instrument and control device carrier assembly , accessory elements , and an electric interconnection group for the instruments , control devices and accessory elements , in the passenger compartment of the motor vehicle , the support group comprising a first support part and a second support part adapted to be adjustably secured together , the first support part being mounted on the steering column of the motor vehicle and the second support part being mounted on the dashboard of the vehicle , the support parts and the components mounted thereon being adapted to be preassembled so that the assembly may be tested prior to installation in the motor vehicle .