If you opened terminal, banged that command in, closed it an the opened MegaTune it would work.
But if it was me doing this, I'd use the VEMS as a very simple ignition controller too:
Use the points as the primary trigger.
Have a fixed ingition table as the advance/retard is handled by the distributor.
Use a single IGBT channel to fire the coil, the firing order is taken care of by the distributor.
This will then give you some context to your fuelling data with at least RPM, but also manifold pressure, and air and coolant temps if you connect the sensors.
It would be fairly straight forward to get the first part working, and the next steps would be incremental.
You may even end up wanting to lock the distributor and try your own ignition curves - copying a known good curve from David Vizard's work would be case of locking the dizzy and banging the numbers in then tuning...