coolant drain plug in the block

Does anyone know where the coolant drain plug is located on the block? I have a '91 4X4 auto w/1.6L engine. I need to drain the block because my radiator has a transmission cooler leak and it is getting very cold outside. I am currently using a heat lamp to maintain warmth under the hood until I can locate the drain plug. The only thing I'm able to see so far is a male threaded allen head plug just forward of the oil pressure sender on the right side of the engine near the front.

according to the gm parts catalogue, the plug just above the oil filter on the drivers side of the block is a drain plug.

Thank you very much. I'll check it out first thing in the morning.