Prestone makes a backflush kit for the cooling system.  The meaningful parts are a tee that splices into a heater hose (three sizes, to fit all heater hoses), a cap for the tee and a coupler to allow connection of a garden hose to flush the system.  It's the only way to go for coolant flushes.  The kit costs around five bucks and is available at mega marts and auto parts chains.  The only reasonable place I could find to put it was in the hose that connects to the end of the head on the driver's side.  Not real easy to get to, but do-able.  See the box in pic at left (the yellow line is the vaccum hose that goes to the hooter valve).   Below is a closer view of the installed tee.  Just cut out a 2" section of the hose, install the tee, tighten the clamps and screw on the cap.  To flush, open the radiator drain, remove the cap from the reservoir, remove the cap from the tee and attach the hose, then run the water for five to ten minutes until the water runs clear.