Harmonic Balancer Recommendations

What are the recommendations on harmonic balancers for a 69 340?
Mine has a dry rotted rubber seal. I've heard it's possible to send it
out for rebuilding which I'd be interested in hearing anyone success story on
the rebuild. Verses the after market balancers? I'm building a mainly street
driven engine that will see a few trips down the local 1/8 mile.