not plugging the head will not cause this, just a massive oil leak
your obviously mixing coolant and oil but it could be caused by several things. 9 out of 10 times its a head gasket tho. what kinda of headgasket and head bolts/studs did you use? did you make sure the head and block decks were flat? did u use the proper torquing sequence/specs? what dowels did you use? if you drilled the head to accept the oem dowels make sure it was drilled deep enough as the dowels could be stopping the head from matting to the block all the way....goodluck tho