Tyler already knows about this but I figured I'd update the thread with the conclusions. FINALLY tore the engine down completely last night. Go figure the failed part is the last exposed. Failed coolant seal like I suspected on the front iron although the extent of the damage is more than I ever expected. Looks like I have a junk iron now...
A closer look:
I'm unsure whether this is the cause of the effect of the overheating event. I plan on returning to the track after the rebuild but I'm now worried about overheating. An upgraded radiator and all new hoses will be installed and I'm also removing heater core so there's no place for the coolant to go except the engine or the radiator. I'd love to underdrive the water pump but there's no way to do that without also underdriving the alternator.