Almost every 103 cylinder head I ever rebuilt or re-surfaced had the gasket blown on #6, exhaust side. If you get a minute pull the spark plugs and compare #6 to the rest. Even just a few drops of coolant will discolor the plug, even if the car is not noticeably using coolant. When you determine it is the gasket, bring it down, I'll fix you up for a fraction of what a shop will charge.
