AFAIK, SC heads use larger head bolts and different gaskets.
According to Fel-Pro, the SC uses different bolts by part number from a 3.8 NA, as an example. SC Fel-Pro head bolts ES72131 are 11mm; NA v-6 Fel-Pro ES72174 are 10.5mm
The gaskets have to do with the coolant flow, SC vs. NA.