[Slam]

Need more info. How do you know it's not the rad or thermostat? Are the cooling fans working? When the car heats up, can you filp on the AC switch and kick in the fans? When you do, does the temp drop? When you bridge the contacts on the thermo switch (top driver's side corner of the rad), do the fans kick in? Is your cooling system pressurising too much when the car heats up? Even timing belt tension can affect temp. Was your trip through the mountains? How's the fuse?

Don't know if I've helped or not, but you may have something to follow to track down your culprit.

HTH