Never heard a 155MM howitzer called a "40 40 mike mike". Where did you come up with THAT crap? And a 155MM howitzer would trash an airfield rather quickly. Properly hidden in the trees around a base, it would be hard to hit. An attack by 155MM field artillery would be devastating. A couple of those in the right place with decent operators could do serious damage.
Most 155MM filed artillery is towed, never seen one mounted in a halftrack. A little research shows an M7 (M7 Priest actually) to be a self propelled gun, 105MM, tracked tank type chassis. Hardly a 155MM howitzer, and certainly not mounted on a halftrack. You could add a towed 155MM howitzer, and have it towed by a halftrack.