coolant leak from back of the engine

I rebuilt my engine from the heads up because it was leaking coolant in the back of the engine. It is a 350 5.7l vortec in my 1998 chevy k2500. I changed the head gaskets and the upper and lower intake manifold gaskets and it still is leaking. it appears to be leaking down rite where the starter is and some streaming down the side of the tranny. My main question is does my year of engine the 98 5.7l 350 have freeze plugs in the back of the engine? Could that be my problem? And if not what else can i look for as a potential leak?.