A quick Mrs. Google search came up with an hour's worth of combat radio chatter. With further digging, I'm sure you could come up with artillery specific chatter, since there are files for air strikes and battlefield. The rub may be that Korean traffic may be harder to come by, to where the Vietnam era traffic is easier to come up with. For all practical purposes, it really wouldn't matter to what era the recording would be from, unless you were to present your vehicle at a MVPA event for judging. Those guys are pretty picky and would deduct points for incorrect presentation.

https://www.youtube.com/watch?v=YzG4RZNLuUk