Twobobs decals for 1/35 AH-1Ws.
Their old sheet is #35-001, "Whiskeys in the Mix", if you can still find it.
They also have a brand-new sheet coming out for a high-vis Supercobra as well, #35-002 "HML/A-169 Shark Mouth Vipers."
Both sheets have black MARINES stenciling and would work great.