Like a bomb went off under the hood...

Why are you seeing so much corrosion in your cooling system? You're not running straight water, are you? Even in climate controlled storage and only driving in the summer you still need anti-cirrosion additives. Preston, Prestone, who needs Prestone?

Something was blocked in your cooling system (or there was trapped air) and it built up pressure which should have been relieved by the cap. (Hint) You're lucky you weren't hanging over the engine compartment when it let go or you could have been severely burned.

Chrysler was very thorough in their engineering and would spend the few extra pennies to make things RIGHT. Over the years I think a lot of this after market latest fad type of sh** became popular to fix shortcomings of pennypinching GM stuff and it spilled over to the Mopar world. My 2 old driver cars with warmed up engines have no problem staying cool. I put 120 miles on my /6 Valiant yesterday (with the top down) in 94 degree heat and it ran flawlessly with the stock radiator and fan. Oh....and a 50/50 mix of coolant.