I was in the guard and was tempted to go army aviation for a minute, and ultimately chose not to for… reasons. But to answer your question: I think you’ll find the Army side is much less of a formal process than the Air Force. Meaning, don’t expect for anyone online to know what units are hiring or when. As far as I’m aware such a site doesn’t exist.
Your best bet would be to have yourself or a very close friend be already in the guard/reserve and start asking around unit leadership. Other than that, you might be stuck relying on a recruiter to at least get the unit names/info for who is flying in your state. From there, I recommend working with a recruiter to get MEPS cleared/ take ASVAB, SIFT and then start sending introduction emails to leadership at flying units, including your SIFT, civilian resume, and maybe a personal statement.