ol' slant is dead... need help!

A whole lot fear mongering. I have overheated a slant many times with no problem. You drove only 1/4 mile? Boiling over didn't hurt engines in the days of cast iron blocks and heads, like yours. The knocking was likely "pinging" which is common when the head gets hot. It sounds like someone tapping the top of the engine with a hammer. It is a combustion event, not metal-metal contact.

It would take a long time for heat to get to the bearings. The pistons would go first since aluminum. I don't think rings could come off in shavings. When they failed in my M-B diesel, they broke in chunks and took pieces of aluminum off around the piston grooves.

Fix the hose, change the oil if it smells burnt. Check fluids. Start it up. Probably no problem. If you still hear knocking, then start worrying.