The 18 series requires modifications in 2 places. Why is that? Because of the priorities?
The first one creates a '#define' used by the INT_LIST, INT_ENABLE and other macros that specifies the PIR reg and bit
Code:
  #define INT1_INT  INTCON3,INT1IF  ;-- INT1 External
The second one adds all the details (PIR intr reg/bit, PIE enable reg/bit, and IPR priority reg/bit)
Code:
  ifdef INT1IF
      INT_Source  INTCON3,INT1IF, INTCON3,INT1IE, INTCON3,INT1IP
  endif
If you're lucky, that's all that's required. However, some of the newer devices like the 18FxxK42 and 18FxxQ43 required some serious modifications to the asm code to make DT_INTS compatible with the register layout and new instructions like MOVFFL, so the 'customization guide' isn't much help with them.