I have a 1987 240 DL non-turbo. I've been rebuilding the engine, and in the process took out my knock sensor and it pretty much crumbled in my hand. It's the single terminal style found here. Not only is it way over priced anywhere that I find it, but no one seems to have it in stock.

I have a friend of the family who has a junk yard full of old Volvos, but every one he looked at had the two terminal style one. So two questions:

1 - Does anyone know the specific year/model this knock sensor is from? My car is a bit of a Frankenstein thanks to the previous owner so I'm not sure if that's why it didn't match when I told him what mine was.
2 - Are the two styles of knock sensors interchangeable? I have to assume that the difference between the single terminal and the double terminal versions is that one of the terminals on the double is ground. Is this true? and if so is that the only difference and I can simply get one of these and connect my original wire to the positive and ground the second terminal somewhere else? (I feel like this is too easy to be true)
3 - Do all single terminal knock sensors act the same? Could I buy a single terminal knock sensor from a different make/model vehicle or would my ECU have no idea how to read it?