Hi, is the motor internal balanced, stock pulleys being used, timing cover?
ATI have a great selection for every application and you can rebuild them. I've run fluid dampers, but went to ATI. superdamper three ring. if your building the motor call them. if your having it build I would suggest letting the builder decide. one note they will not fit out of the box they are reemed to fit for perfect fit
http://www.atiracing.com/products/dampers/charts/damchrysler.htm
If you use the ATI Super Damper, be aware you'll need a different crank pulley. I ended up using a March w/spacer. Cheaper and less work than spacing everything else out 11/16" .
Are you running the stock timing cover, and stock pulley location