So when replacing the Coil, I just swapped like for like with the connections without any concerns.
But having read recently that a car swapped from + Earth to - Earth would still run without changing the coil connections, I thought I'd check... yep, they were incorrect, perhaps they had been since the new loom was installed when it was rebuilt 20 years ago.
I came across a quick check on a Lotus Cortina website, which I thought I'd try, and it worked; so I thought I'd share it here.
Now what I will say, is that this text is actually repeated on several websites dealing with vintage cars, and is clearly a copy n'paste from somewhere as every example I found used the same American spelling for 'Center' .Testing Ignition Coil Wiring Reversal.
You REALLY need to test this. With the ignition off, engine off, pull a spark plug wire loose from a spark plug. Place it loosely back in place.
Now start the engine. Hold a no.2 lead pencil carefully in one hand. With the other hand, pull the loosened spark plug wire slowly away from the plug. You shoud see a good size spark jumping from the wire to the plug. Now... CAREFULLY place the sharpened lead point of the pencil into the path of the spark... you should see a "flare" of particles flying from the pencil lead TOWARDS the spark plug. If you see a "flare" of particles flying from the pencil lead TOWARDS the wire... you have the coil hooked up backwards. Remove the pencil lead from the spark path. Replace the wire. Shut the engine off, and re-reverse the coil low-tension wires and re-test. Get it right!
Why does this matter? If you got this wrong, you will be losing about 50% of your voltage at the spark plugs! Weak spark! Essentially, if the ignition low tension coil wiring is reversed, the coil will... "pull" spark, rather than... "push" the spark. Electrons prefer to leave a high-temperature (high energy) surface (like the centre electrode of the spark plug) rather than a low-temperature (low energy) surface (like the arm of the spark plug). More voltage (more spark) is available if the electrons move in the correct direction, in the direction they prefer, from the high-temperature centre electrode of the spark plug to the (relatively) low-temperature arm of the spark plug. Test it! Get it right!
Irrespective of the stuff about 'pushing v pulling' the spark (i gave up trying to think about how it would work on a +ve Earth car), if the White and White/Black are not changed over when reversing the system polarity, the spark is jumping in reverse, because that pencil lead in the spark path trick actually works and gives a little orange flare in the direction of the spark jump.
Apologies if this is old news to everyone, it was new to me and I found it a nice little thing to try.