Thanks for all the input guys....got a lot of good tips for future reference!

I think I fixed the problem. I removed the drain plugs on the engine block (full of crap!) and flushed the engine till they ran clear. Then I bought a prestone flush kit and ran it thru the radiator and engine. Then drained and flushed again with water....drained and added antifreeze. Took her for a nice ride (about 30 miles) and no more overheating!! Seems to be fixed! Thanks again for all the help!