Whether you are rebuilding the complete engine or just overhauling the balancer assembly, the associated parts should be renewed, preferably replacing all the interfacing parts at the same time - mixing worn parts with new can lead to premature wear of the new item; even the knowledge that old parts have been reused can be stressful!
Big four cylinder engines rely on the balancer assembly to smooth out the inherent primary and secondary vibration and so is vital for reliability and performance.
Other parts of the vital balance assembly you may wish to consider:
Renewing all the parts of the balancer assembly at the same time is advisable. Add as many items as you wish to the same shopping cart, new fasteners, gaskets and O-ring seals for example, and still only pay the same fixed price shipping cost.