I agree with what's been said here. But looking at the pic of the rubber freeze plug, that is way thicker than a standard plug. It could very possibly be blocking flow. I would fix that, put a spring in the lower hose. You get them from mustang suppliers. I'm told you can't see the hose suck closed because it only does it while driving. And fling that stupid fan as far as you can. You need a mechanical fan and shroud. Period. You will have to possibly make a shroud. I suggest using the Summit stainless steel fan. It's about $40. If you don't like that, the Mopar thermostatic clutch fan works awesome The fan needs to be 1/2 way in the shroud. This is the basics that have to be done first. Also, make sure the hood to radiator seal is in place. And I put the thermostat in a pot of water and verified the opening. I went through all this with my Dart. The answer is not one thing it's alot of little things that together will solve your problem.