Never saw this before, plastic end of radiator, back BLEW out, top to bottom, 1999 3.8L. Daughter drove in town 2 mile2, no coolant. Engine knocking when she go home, how bad the damage to engine?

 

engine knocking? she probably toasted the engine. Sometimes all you need is a Cylinder head rebuilt, but if it over heat bad enough, the Valve seat would drop, and your engine is a boat anchor now.
but on the positive note, Used 3.8 engine are plenty in the salvage yard, and cheap.