A bit about coils: The sports coil produces a higher voltage at the spark plug. The standard setup on most 4 cylinder P6's is to use a ballast resister and a 1.5ohm coil (Measured across the low tension spade connectors on the coil). The idea is that the coil runs at aorund 9 volts under running conditions, but will have a 12 volt supply when cranking on the starter motor.
Non-ballasted coils have a resistance of around 3 ohms (Measured across the low tension spade connectors on the coil). These are designed to use 12 volts under all conditions (running and starting).
So, you can bypass the resister with a 1.5ohm coil, but it will run hot and may well burn itself out. If so, you would want to fit a 3 ohm coil as a replacement.
To make things a little more complex, Rover in its infinite wisdom decided to hide the ballast resister inside the wiring loom from the points to the coil negative terminal (via the tachmeter if fitted). After 40 odd years they tend to burn out causing the ignition to stop working. That happened on my car and I replaced the wire without a ballast resister and put in a 3 ohm Pertronix flamethrower coil.
You may find the the electronic dissy will expect a 12v supply. In which case you'll need to by-pass the resister in the loom anyways. You'd also want to fit a 3 ohm coil as a 1.5 ohm coil will unduely stress the module in the dissy.
I hope my witterings make some sort of sense?
Best,
Steven