You are correct there are two outputs from the VSSB to PCM(s) 6395 or 7427. One is trans output speed at 40 pulses per revolution (PPR) and the other is vehicle speed at 2000 pusles per mile (PPM). The DRAC has the same two signal at different pin locations. So with some repining DRAC and VSSB can be used interchangeably but with the DRAC if you are using an electronic speedo then you will need a VSSB because the DRAC does not have enough outputs for the PCM and speedo. Just FYI the speedo output is at 2000 PPM just like the vehicle speed input to the PCM.