There's a small possibility it could be an Atari Shark Jaws as well... though as the joystick and buttons on Caveman Ninja line up with where the sticks were on Tank II, I tend to think it's a Tank II as well.
sad looking conversion. I do kinda want Caveman Ninja but I'd probably put it in a generic Data East cab. I'm still new but it does look abit like the tank cab