Federal regulations generally require vehicles to meet emission standards, and those standards usually necessitate all original emission control equipment being present and functional. A 1992 F-150 likely had dual catalytic converters for better emission control. Removing or disabling one would violate those regulations, making it illegal at the federal level and likely at the state level as well.
This could result in failure of emissions testing (if your area requires it) and potential fines. You'll need to have both catalytic converters functioning correctly to pass emissions.
