New damper/balancer?

You don't a high price dampener/or balancer for external bal motors] you just need one in good shape. And you don't need to turn 6k in a 360 to make 350hp if the parts/combo's there, so thats another indicator of how much more than usual attention this area of your build needs.

I do agree that the summit piece is of quality and fairly priced for what you get.
The last dampener I bought was a redone stock dampener and only cost $50, I run my stuff hard..to say the least.

Remember....stock 340's factory advertised to spin 6k with warranty used stock balancer, not sfi and not hundreds of dollars either.