Me too!
Heat Problem Solved! Contrary to my post above, I discovered on closer examination that my brief hosing of the front of the cooling elements was in No Way cleaning them out.
I towed an empty horse trailer in the mountains this weekend and the heat problem seemed to be worsening. Unless I ran the heater full blast, I was having a hard time keeping below redline on any kind of hill. I got around to looking BETWEEN the cooling elements and found what others have discussed above. The front part of the radiator was completely plugged dirt and weeds. It seemed to be in a circle corresponding to the fan diameter.
For a temporary fix, I went to a car wash and was able to spray out all of the visible crud. There's not a lot of good angles to spray from, but the stuff I got out didn't seem too stubborn and appeared to come right out. For the remainder of the drive home, I was almost always at 180 deg (have a 180 t-stat), some hill climbs brought it to 190, and on one deliberately severe test (big hill climb, WOT, with comp at 5x5 to pass a string of SUVs) I saw it go to almost 200.
I'm sure this hurried job was in no way an adequate cleaning, but now I know where the problem lies. What a relief. I drive an average of 200 miles of dirt road a month - I think this will become part of my routine maintenance from now on.