240 D block heater location

I'm looking to put a block heater on my 82 240D No love starting at 5F
or less w/ Rotella 15W40 in the crankase. Is the magnetic better or
worse than the plug?

And the plug, where does it go on the engine?

If you have a heater installed, the plug is most likely routed to your
bumper by the tow hook. Otherwise, I hear that it is hard to install it as
the bolt where the heater hooks up are rusted in place.