Something does seem to be messed up between the data sheet and the micrchip *.inc.
Anyways, this compiles in code space with MCS
Code:
@ __config _CONFIG1, _EXTCLK & _WDT_ON & _CP_OFF
and when the hex is imported into MPLAB it shows the Oscillator as
EXTCLK as Port IO.

Other than that I do not have a way to test, do not have that chip.