Well, if you have it with a JAMMA game, you can sometimes just change a dip switch to flip the image.
Other than that, this is how you do it for a G07:
Your yoke connector has 4 wires connected to five pins:
5 4 3 2 1
The horizontal yoke (red and white wires) is connected to pins 1 and 4.
The vertical yoke (brown and grey wires) is connected to pins 3 and 5.
To flip the image, just reverse the positions of each set. For example, if you have the red wire on 1 and the white wire on 3, then move the red wire to 3 and the white wire to 1.
Whatever you do, do NOT put a horizontal wire on a vertical pin, or vice versa, as you'll blow the yoke and maybe damage the chassis...