I doubt Peter's suggestion of a reader will work with 3.7 Roadster ECU but would be interested to know if it does.
Adrian. I am reasonably certain that the standard ECU would be readable for road speed on the OBD II port, it should be. But with the MBE ECU upgrade it would depend whether or not they are still using the original ECU for dash functions, and if not whether or not the new ECU is connected to the OBD II port.