I would try using a gatling gun instead of a regular machine gun. Take some plastic that is thin and narrow for a mount and judge the size of the plastic that looks best. Cut the narrow plastic to your "realistic" specifications and paint olive drab. The size of your mount will be trial and error. Use different size plastic to judge. Then super glue your gatling to the mount facing outside. this would be a fixed mount. For a swivel mount, cannabalize the main m-60 mount on the Seal tactical jeep. order two from small joes, their 7.95 a piece. Then cut the tripod mount, judge the correct height, then glue.