modified Units:
The UH-1 ARA "Hog"
A huey with a total of 48 2.75 FFAR's used quite extensively in the 1st cavs battles around LZ X-ray, normally taking over from the Tube arty to cover the final approach of the Slicks. Then to provide close air support to the Infantry once on the ground.
Normal Mode of operation was to dump half the rockets carried in one go at an area around the LZ to keep the NVA's heads down while the Slicks unload. Then to use the rest in support of the infantry.
IT was named the Hog because due to the massive weight of the rocket packs it was very sluggish.
To model this accurately I would have preferred to create a separate unit, and weapons in the OOB, but we're not allowed to.
So, to use in a senario:
Get a UH1 Gunship, change all 4 weapon slots to weapon #148 (4x FFAR), and give each weapon 3 rounds of HE ammo. However that doesn't work as good as it could, as It only really suppresses the unit it's aimed at.
On a side note If you need something more fancy for you helicopter gunships:
http://tri.army.mil/LC/CS/csa/aahist2.htm#UH1M
In fact that page seems to cover most Helicopters in the period, even if not in detail.