First, go to the 18F1320.inc file in the PBP directory and comment the comment the config lines so it looks like this. Now the configs can be played with in code space.
Code:
       NOLIST
    ifdef PM_USED
        LIST
        "Error: PM does not support this device.  Use MPASM."
        NOLIST
    else
        LIST
        LIST p = 18F1320, r = dec, w = -311, w = -230, f = inhx32
        INCLUDE "P18F1320.INC"  ; MPASM  Header
  ;      __CONFIG    _CONFIG1H, _XT_OSC_1H
  ;      __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  ;      __CONFIG    _CONFIG4L, _LVP_OFF_4L
        NOLIST
    endif
        LIST
EEPROM_START	EQU	0F00000h
BLOCK_SIZE	EQU	8
Now go to the MPASM directory and open the P18F1320.inc and near the EOF you will find all of the possible config options and in this one there is even a sample. Copy the sample to the top of your code.
For now change the CONFIG1H and CONFIG3H to match below. You can do other changes as needed.
Code:
'18F1320 INTERNAL OSC RUNNING AT 8MHZ - MCLR AS INPUT AND OSC PINS AS INPUTS
@ __CONFIG  _CONFIG1H, _INTIO2_OSC_1H & _FSCM_OFF_1H & _RC_OSC_1H
@ __CONFIG  _CONFIG2L, _PWRT_ON_2L & _BOR_OFF_2L & _BORV_27_2L
@ __CONFIG  _CONFIG2H, _WDT_OFF_2H & _WDTPS_32K_2H
@ __CONFIG  _CONFIG3H, _MCLRE_OFF_3H
@ __CONFIG  _CONFIG4L, _DEBUG_OFF_4L & _LVP_ON_4L & _STVR_ON_4L
@ __CONFIG  _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L
@ __CONFIG  _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
@ __CONFIG  _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L
@ __CONFIG  _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
@ __CONFIG  _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L
@ __CONFIG  _CONFIG7H, _EBTRB_OFF_7H

OSCCON=%01110000
DEFINE OSC 8
Now if you want to run at 40MHz you will need an external crystal or resonator running at 10MHz.
Changing the first line of the configs.
Code:
'18F1320 EXTERNAL OSC RUNNING AT 10MHZ PLL TO 40MHZ - MCLR AS INPUT AND OSC PINS AS INPUTS
@ __CONFIG  _CONFIG1H, _HSPLL_OSC_1H & _FSCM_OFF_1H & _RC_OSC_1H
@ __CONFIG  _CONFIG2L, _PWRT_ON_2L & _BOR_OFF_2L & _BORV_27_2L
@ __CONFIG  _CONFIG2H, _WDT_OFF_2H & _WDTPS_32K_2H
@ __CONFIG  _CONFIG3H, _MCLRE_OFF_3H
@ __CONFIG  _CONFIG4L, _DEBUG_OFF_4L & _LVP_ON_4L & _STVR_ON_4L
@ __CONFIG  _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L
@ __CONFIG  _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
@ __CONFIG  _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L
@ __CONFIG  _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
@ __CONFIG  _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L
@ __CONFIG  _CONFIG7H, _EBTRB_OFF_7H

DEFINE OSC 40
That should do it if I did not screw something up ....