1970 340 Balance Problem...Bottom Line

I have a Pioneer SFI neutral balanced balancer/damper on my car. Jegs sells them under their own label. Not sure who makes their non-SFI balancers. But for long term use, most aftermarket units should work well and they are new as opposed to old, used OEM units.

Summit has the Pioneer "Street" harmonic dampers.

As for the rear seal, hopefully it's the pan seal and not the rear crank/main seal!