Until around 2002 the electric code was whatever the local AHJ said it was in Florida. Jurisdictions being 2 or 3 cycles behind was common and some were farther behind than that.
It would not be surprising that a house built in 78 was not built to the 75 code when GFCIs started showing up. Out in the hinterlands enforcement was spotty anyway.
There were also additional local rules in some places. It was this mish mash of local codes that prompted Florida to pass the Unified Building Code law. Now everyone is required to enforce the state code.
