Right by the thermostat housing int he front left of the motor like you suspected. As you look at the thermostat housing it is at about the 6 O'clock position. I am not sure why your boiling over but maybe you just changed the coolant and need to bleed the air out of the block. There is a bleeder bolt at about 12 O'clock on top of the thermostat housing. If the Head casting is good. if not like my 06 there is a pretty bolt holding/plugging nothing on my Head