Coolant Leaking problems of the 1999 Ford Taurus

I have a 1999 Ford Taurus wagon and the cooling system has been a thorn in my side for the last 2 years. First 1k was leaking coolant and when I brought into the dealership,was told the freeze plugs needed to be replaced as the coolant was acidic. This was my fourth car and I had never in my life heard anything like that. Then, when changed there was alot of rust in the coolant system. Had to change the thermostat, freeze plugs, and water pump. Then things became worse. I started having engine problems which resulted in replacing the head gasket and engine head. When I took the car to the dealership, I was told they have seen this problem many times on that model year car. They suggested I replace the engine, at an estimated cost of $7,000 or buy a new car. Then I had no heat in the car as a result also. Needless to say, I have gotten the work done on the car and spent about $4,000. I was told by one dealership there was a problem with the engine core which was a manufacturer defect but Ford would never own up to it.