I'm new to the Volvo world, but I own an '59 MGA on which I run a 3 ohm Lucas sport coil. This is a coil designed for a 12 volts non-ballasted ignition system. The coil has a primary resistance of about 3.2 ohms. A coil for ballasted ignition system will have primary resistance of about 1.6 ohms.
You can measure the coil with an ohmmeter or multimeter.
In my experience, when a coil is too hot to the touch, it is failing. Inside the coil is an oil that is supposed to keep the coil cool. When this gets so hot that one can't touch the coil, there is something wrong internally and it may only be a matter of time before there is complete failure. My cases have usually started with a misfire under load.
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