Toyota Repair: Coolant leak, intake manifold gasket, coolant leak

Question
'86 Toy P/U 4X4  251K mi 22r

Bad coolant leak (1 gall every 7-10 days). Original leak was freeze plug - replaced that.  Soon thereafter a worse leak (volume)began. Appears to be coming from high on exhaust manifold side (above freeze plugs). Is dripping on manifold/exhaust somewhere because produces much steam (coolant odor). Head gasket? No evidence of coolant in oil (been watching that closely); no vapor or odor in cabin; little heat from heater.  Heater core?  How begin to diagnose?

Answer
Check at the rear of the cylinder head for the leak, there is a aluminum plate that exhaust gases pass through to cool the egr valve, if the leak is firther foreward it could be the headgasket or the intake manifold gasket, coolant also passes through the intake manifold.