Like a bomb went off under the hood...

I let a day or two pass before writing this because I still don't know what happened. Here it goes...

Our 340 doesn't get run much, in fact it only gets out at most once or twice a year usually it just sits in a climate controlled garage...As such, I began to notice a considerable amount of antifreeze had built up (crystallized) around the intake water neck. Two weeks ago I took the car for a drive and lo and behold it began to overheat badly...So much so that it was getting blown out of the overflow tube and trailing on the ground into the driveway. I looked at the temp guage (factory) and it was nearly spiked. I blew water through the radiator with a garden hose and finally got the temp down and I parked it. Later I pulled the thermostat and found it was completely corroded...Last Saturday I replaced the thermostat and the water neck housing with another one that I had laying around. I cleaned everything up and even used a new band clamp instead of the factory squeeze type that was on it to safely secure it (or so I thought). I filled the system, took it for a short spin around the block and brought it back home. Once it cooled down I topped off the radiator and took it for a 2 mile trip....bad idea. About 1/2 way into it after it had reached operating temp I noticed the gauge was creeping up once again (ambient air temp was 80*) ....by the time I got it home it was holding steady but up in the range... I coasted the car into the driveway and let it sit- engine off...A few minutes later all hell broke loose...There was a small explosion under the hood and the steam began to roll. The force was unbelievable. It turns out that the top radiator hose blew off at the water neck and spewed antifreeze all over the underwood area...and I mean everywhere! I can honestly say it was so violent that if the hood had been open at the time I would have been scalded badly...The car runs and accelerates, no miss, no antifreeze in the oil, no leaks.

So here I am....asking for help. Has anyone ever had this happen before? The car was completely restored in 2001 with everything new or replaced. I have a 160* T-stat in it with a flow-cooler water pump, radiator was recored, etc. In the early years after it was restored we had drove the car well over 100 miles one way with no issues. Where do I begin? Collapsed lower hose, plugged radiator? HELP!