Harmonic Balancers

I have a Rattler on my 340 in my 74 Sebring Plus, been on a long time and I think the only issue was I had to drill a hole bigger in my stock crank pulley. I have March pulleys on it now and they work fine, belts line up good and no issues there...I kinda like how it “rattles” and real low idle when it’s cold or as it shuts down, people always think somethings wrong lol

I have a fluidampr for the 340 in my Valiant but never installed it....the China made elcheapo is working fine. I do know I need to run a different stock crank pulley, I got the pulley but can’t remember it’s appliction, think it was from a 68-69 273 single groove.