Proper installation of block heater

[Brent]

I purchased a block heater that fits into one of the plugs on the right side of the block. I have reviewed the repair manuals and think I know how to drain the coolant. Where does one install the block heater - into which plug? I see there are a number of round plugs and don't want to go banging on something that shouldn't be knocked out. Are they all the same? Pictures are welcome if you have time or have something handy that you've done before.

[v8volvo]

There is a correct plug to install it into. I don't remember which one off the top of my head, but have an engine on the stand at work that has a heater in it that I can look at tomorrow. Will do so and post proper info here.

[Brent]

Thanks! Looking forward to learning which plug!!!