I'm using a 616 out of a 1980 240D, and not being an expert with these motors, I thought I'd ask about the block heater! On the right side of the motor in the rear freeze plug hole on the block is a plug with two prongs. I can only assume that this is the block heater? Will the plug sold on this site work with that heater assembly? Is that all there is, just plug into the block, and the other end in the wall outlet?

Sorry for the rediculous question.

NOt a ridiculous question, just that its a long time before winter, eh?
Well, that sounds like the 2-pin block heater that is usually found on the diesels but without a picture its hard to say for sure. If the one sold on Fast lane looks the same, then it probably is.
You just plug it in, right. Some people use a timer so it comes on a couple hours before you plan to use the car, saves energy. If its really cold you would want to run it continuously I suppose. I only plugged mine in on trips where its below freezing

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Thanks! It's great to know that all I need is a plug! Thanks again for the info...

You may want to check the resistance across the prongs to make sure you get some finite resistance. These heaters use about 400W, so I would guess the resistance will be about 36 Ohms.