LZ-Xray
http://www.lzxray.com/
Advice from Gen Hal Moore (for storyline?)
http://www.au.af.mil/au/awc/awcgate/documents/moore.htm
Btw:
I got an idea of adding real radio chatter to the background of mission briefings.
USMC combat helicopter accociation
(Audio/Video recordings from combat mission at the end of the page. The mainpage has links to anything helo related in vietnam)
http://www.popasmoke.com/audio/
Sights and Sounds from the War in Vietnam
101st Airborne Division
(more combat audio clips)
http://www.cyhaus.com/vietnam/default.htm