I'd go with an ATI damper. Using one on the 340 I'm getting ready to fire up. The engine shop I use swears by them. Also, I used one on the little mini-stock 4 banger I raced, turning 8500 rpm's at corner entry. With all the inherent vibrations in those engines, once I switched to an ATI damper I got 2 seasons before a rebuild, compared to rebuilding every season without that damper. Bearing wear was minimal.