Joe,
Firstly, welcome to the forum! Gino's got it, the 1-151st Aviation of the SC ARNG flies the gray Apaches. Two of my buddies here at flight school are in that unit. They fly A models, but they are extremely late ones. The one profiled in my book is 94-0332, from the last production block of US A models. I'm slowly but surely working on a Revell 32nd scale kit that I'll be building as one bird from this unit as well. It won't be 332, but another bird with similar, but more interesting markings.
There have been rumblings that the gray scheme may go Army-wide. I certainly hope so, as they're a LOT harder to see than a great green hole in the sky coming towards you!