Julian: The knock you heard was probably the piston striking the bottom of the head. Once the bearing is out of there, the piston moves up farther in the bore, eating up deck clearance. Oil pressure, once it burps for an instant, the rod bearings go first. We had this happen on a 302 in a Group 7 McLaren. We were spinning it up to 9,000 rpm when the oil-filter seal blew out. It actually blued the big end of the rod. We turned the crank 0.010 under and reused it. Only the rod and piston needed replacing. Chances are your crank is okay, but it should be checked for straightness. Also check the mains to make sure they are still straight.
Check the picture. This is a Carrillo rod we just pulled out of a 351. The bearing had standard oil clearances and the engine wasn't turning over 8,500 rpm when the bearing grabbed the journal and broke the cap bolts. The cause was super low viscosity oil being used for qualifying. Squeezed out the oil under load and it was metal to metal . . . bang. The crank is being reused, but the rod and piston is junk.
