Sounds like to me that the radiator could be the culprit, you say that the rad was flushed, but do you know for sure that the radiator doesn't have restictions? And moreover, when does the car overheat, at idle, during crusing, or both? The answer to these questions will give us a better diagnosis.
The upper hose issue is a bit weird, but if you remove the pressure when hot then recap and fire away, the cooling will produce a vacuum and MAY collapse due to flow and cooling, but if the cap is vented when you are running and getting the collapse, then it sure sounds like the pump is running the wrong way? The hose should not collapse when running, even if bad.
So, check the thermostat to make sure it's opening, the pump is correct, the radiator has sufficient flow and the hose issue last.
SOUTHEASTERN GOODGUYS REP
[This message has been edited by HOTRODSRJ (edited 11-24-2001).]