did you keep up on your coolant additives? you may NOT have a bad head gasket but a perforated cylinder liner from the cavitation of the coolant eroding the cast iron cylinder liner. 7.3's RARELY blow head gaskets. RARELY!
the end result is the same however, a pinhole in the cylinder wall allows pressurization of the coolant.
putting in new liners can be done, but its not cheap and you still have the same worn motor. you still have to pull the motor and strip it down. you are better off getting a SB or LB.
that sux either way.
dp