The 7.3 heads have the cooling passages in the corners plugged, so the gaskets have no provision for coolant flow there. Those passages are where your coolant is leaking. I think they plugged the 7.3 passages to get away from the leakage problem. Some have speculated about drilling holes in the plugs and using 6.9 gaskets to improve cooling but I don't know if it has been done. Icanfixall posted a good picture comparing the two gaskets. http://www.oilburners.net/forums/showthread.php?70885-Disappiontment-In-The-Mountains/page5