I found a die cast Loach/Cayuse OH-6 helicopter toy closely scaled for 15mm in my local dollar store so grabbed a couple for $2 each (nothing in the dollar store is a dollar anymore...). It has some goofy markings and is missing some detail.
Here is before (left) and after (right) being airbrushed with primer, then olive drab, and the window gaps filled and painted blue.
The minigun comes from the AH-1 cobra sprue from Team Yankee where it is an option for doing an earlier Vietnam era version. I think it will stand in just fine for Vietnam or early Cold War games.