zumo,
when my straight six went, it wasnt a rod. the head dropped a valve, which knocked around in the piston cylinder for about 30 seconds, and then rammed itself into the side of the front cylinder wall. (this consequently shattered the piston, dropped the piston rod, which rammed up into the bottom of the block). anyways, i pulled the head, and found an additional two valves were completely frozen.
because of that whole experience, i believe upgrading the heads is the way to go. hopefully, there isnt any damage to the block. but as long as that engine is knocking, DONT RUN IT if you can avoid it!
good luck tearin her apart, and let us know what the outcome is!
jewels.
