hmm.
my 289 would overheat frequently as well. i did the following:
- had the radiator cleaned and rodded
- replaced the heater core
- replaced the radiator intake/return hoses (only the intake has the spring tim)
- installed a gano filter (return hose)
- replaced thermostat
this helped the car quite a bit, but it was still a little warmer than i wanted.
i had a problem with a head gasket, so i decided to replace both of them. turned out that when i took the heads off and inspected the gaskets, both gaskets had no holes for the passages in the front of the head. that's right, they were blocked, which meant that water was travelling through only one side of the head!
these were not the original head gaskets, but fel-pro replacements. the new gaskets i bought were the exact same way! i wound up marking the holes that should have been on the gasket to begin with, cut them out, and reinstalled them and the heads.
when i was done, the car stayed nice and cool, very rarely going above 1/3 on the temp gauge unless i was in summer stop-and-go (and only then did it ever get close to halfway).
HTH.
