My 245 came with one. It is a simple setup. It replaces a frost plug and the cord runs to the front of the car where it dangles to be plugged in.

I seldom use it, though, as the car starts in most cold weather and I'm the kind who doesn't mind a bit of cold in the cabin. But if you like to leave your car idling until it warms up, then a block heater on a timer is a good thing.

There are a couple of other kinds. One appears to clamp on to the block and use some kind of magnetic system to warm the water/engine, the other is installed into a cooling system hose and circulates the water (this may impede flow when not running).
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.