Pi3 plus vga666 outputting 640x480 31k help

[MAME TIME]

Hey guys

I'm running emulation station/retroarch and I'm trying to output through the gert vga666 in 640x480 in 31khz to an arcade monitor and I was just wondering which values would be required? I'll post my config shortly, but any help would be greatly appreciated 

[MAME TIME]

BTW disable SPI and IC2

heres my config

# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1

# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
disable_overscan=1

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#config_hdmi_boost=6
#hdmi_ignore_edid=0xa5000080
#hdmi_group=2
#hdmi_mode=4

#this was added to force vga note 640x480 60hz
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1

dpi_group=2
dpi_mode=4

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

# Uncomment some or all of these to enable the optional hardware interfaces
dtparam=i2c_arm=off
#dtparam=i2s=on
dtparam=spi=off

# Uncomment this to enable the lirc-rpi module
#dtoverlay=lirc-rpi

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=on
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=256
overscan_scale=1

# Pretends no audio formats are supported by HDMI display, forcing all sound out the 3.5mm headphone jack.
# May not be needed for all HDMI devices
#this was turned on to enable the 3.5 audio jack
hdmi_ignore_edid_audio=1