Three weeks ago I purchased a 2 owner 1984 K5 Blazer with a crate 350. The second owner did nothing except drive it for years and years, never changed the oil, never even put antifreeze in the cooling system. So I changed the oil, and the engine consumes a bit, but I just put four thousand miles on it driving from San Francisco to New York, and even though it was a gas guzzler with a rebuilt 700 R4 and 3.08 gears, it made the trip without any issues. What concerns me is the radiator was full full full of rust rust rust. I drained and refilled it several times along the way, even twice was able to get hold of a garden hose and flush the cooling system using the T adapter someone had installed in one of the heater hoses. So the rust is much less severe now that I'm home, and I did twice add Red Devil radiator cleaner, and a couple days ago a bottle of Prestone radiator rust cleaner. Yesterday I removed the overflow bottle, and.there was 1/4" of rust at the bottom. So it's pretty obvious the system has more rust than metal. But luckily the tstat was removed before I bought it, and it never ran more than 130 degrees. I flushed the radiator with thousands of gallons of water, and the heater core and the block with the T fitting, and the water runs much less rusty. Any suggestions before I replace the tstat and coolant?