I found a great running 235 that does not smoke to replace the tired old 235 in my 1959 1/2 ton. But the new motor has a very loose harmonic balancer (like really loose I can easily move it with my hands)

How much of a can of worms could I be getting into with the loose harmonic balancer? How hard are they to replace and are they typically OK after replacement or are they prone to getting loose again after it happens a first time?

Thanks for any help

Dave