Under the exhaust manifold (do it when the engine's cold unless you like burns ), there should be a very large bolt head (for putting a block heater in) and just above or just below that should be the drain plug. I'll see if I can find a pic.
I think my B engine has that little plug below the big one too, however, IIRC the hole in the block doesnt actually go all the way through - so its not actually any use as a drain! (its just an external hole which is plugged by that nut)
The first picture is for a late 900 block as it has the extra thing that bolts on with three bolts (and that's the type I have on Blu'y now - much easier to get to the drain!). The second picture looks about right.