340 Harmonic Balancer Recomendation

Buy a balancer for what youre doing.
If youre racing, great.. buy a high dollar fluid dampener, ati, etc

If youre just hot rodding or hitting the strip once in a while go buy a pioneer brand.
There is such a thing as overkill...and a cast crank 340 with fluid dampener 'that isnt in competition racing' is a good example of just that.
I really don't know all of what you're doing so I might not be spot-on. But unless it's Concours restoration I think I'd get a lighter piston and just use something like a #357 318 police crank... or just a regular cast crank and balance it up neutral...