Still FRICKIN Hot.... what about Aluminium Radiators

[CobraEd]

This seems to be a common thig with 428s. Here is the same problem from someone else I found on the Internet.

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Hi All,
Got a major problem and thought someone might have the knowledge to
help. My 69 Mach 1, 428 CJ which I bought last year has been giving me
fits with overheating. If I drive a mile, the gauge peaks past the red
line. I have replaced the water pump, clutch fan and thermostat, and had
the radiator flushed (they said it looked good). If I pull the
thermostat, it will stay in the upper portion of the gauge a little
below the red line but can still get pretty close to overheating at
times. I used a temp probe gauge to check the temps of both heads. I
probed just above each exhaust port on all cylinders. The left side all
ran between 210 and 220 degrees. But the right side ran beween 260 and
280 degrees. I had read where the head gaskets have been accidently
placed backwards and have cut off the water flow through the head. I
thought this might have been the problem with the right head. I just
pulled the intake manifold and right head. The gasket is on correctly
and I don't really see a problem with the head or gasket. Can anyone
help me? I'm at a loss and don't want to put it back together until I
can figure out what the problem is. The weather is getting nice and I'm
getting anxious! Thanks in advance.