All slant sixes both cast and forged cranks are internally balanced, so you don't have to worry about THAT. From there, it's simply personal preference. For general street performance, I would get something like this.
DODGE PowerBond PB1001N PowerBond Premium OEM Replacement Harmonic Balancers | Summit Racing
If you think that's not enough, there's always this. There are American dealers as well.
Romac Performance Series Harmonic Balancer : Steel/Steel : suit Slant 6 225ci (timing case with spot-welded timing tab)
