1997 Dodge Intrepid oil light and over heating

What would make this cars oil light come on even after putting in two oil sending units, the car starts to overheat and cause the coolant to overflow? Could it be the oil pump going bad?

It could be lots of things, including a bad oil pump. After the first sending unit you should have checked the oil pressure with a real gauge. Running this long enough to make it over heat with low or no oil pressure could have trashed your engine. Good luck.

Blown head gasket?

Has the obvious been checked yet, like perhaps a stuck thermostat? Unfortunately that wouldn’t really explain the oil light. You need to have the engine’s oil pressure checked with a gauge when it is warmed up.