Claymore,
Ok, I'll give you what help I can. Firstly, the 1st Cav wasn't in-country after the summer of 71. The 3rd brigade was left in Vietnam, but reorganized as a "mini-cav division", with all the recon, artillery, infantry and aviation assets a division would have, but on a smaller scale.
That being said, the aviation assets remaining in-country after August of 1971 were:
F/79th Aerial Field Artillery (Formerly C Battery, 2/20 Aerial Rocket Artillery "Blue Max")
D/229th Assault helicopter Battalion (which was reorganized into F Troop, 9th Cav)
The "Blue Max" guys were flying the AH-1G Cobra and were the de-facto close air support for the ground forces in III Corps
F/9th Cav was the eyes and ears for III Corps. They were equipped with three platoons, scouts (white), slicks (blue) and guns (red), or OH-6s, UH-1D/Hs and AH-1Gs. The idea was, the scouts would find the bad guys, the guns would waste em, and the slicks would insert the aero-rifle, or Blue platoon to see if anything was left.
The closing months of the Vietnam war are fascinating to study, because so much was done with relatively little. Those US troops still in-country were trying to stay alive while the bad-guys were doing everything they could to disagree with that idea.
New innovations were created out of necessity, including the SA-7 Suppression kits, HEAT rockets and even the TOW missile system (although these didn't appear on the Cobra until after Vietnam), but believe it or not, UH-1Bs flew with TOW systems in 1972 and were VERY effective against the North's tanks.
I actually cover a considerable amount of the last two years of the war in my book on the Cobra from Osprey. It'll be out in stores in 3 weeks.
If I can be of any further help, drop me an email!