Cooling Issue - 1964 Dart GT - 273 with automatic and A/C

'Collapsed rad hose' is largely a myth. The upper hose would never collapse, and the only reason why the lower hose could collapse is if there is severe clogging or restriction in the radiator or thermostat—and the hose would then un-collapse once the system heats up and builds pressure.

I don't claim it can't happen—only that it is exceedingly rare and has one specific cause. Think it over: that bottom hose runs from the radiator outlet to the water pump inlet. The only way for there to be negative pressure in that hose is for there to be extreme restriction upstream of that hose so the water pump pulls a vacuum, and the hose would have to be weak/soft, and there'd have to be no/low pressure in the system as a whole.

That spring that used to come in some rad hoses was meant to keep the hose from kinking if overbent. Cut the hose to length (as required) and install it properly, and have good engine mounts, and there won't be any kinky stuff happening.
Sorry Slant six, it's not a myth, that is why I mentioned it. It has happened to me years ago. Not only did the hose suck in, but I had to pull the water pump to take the spring out of it. It is true as you say that a restriction ahead of the hose could also collapse the hose, if the spring or hose became weak. My point being, over heating can be caused by many things, as many here mentioned. I just added another possibility.