Shake rattle and roll

I would take a serpentine Magnum balancer and your universal one to a machine shop and see if they can make them match.
Universal usually means it doesn't fit anything..
I accidentally ran mismatched flywheels and balancers because apparently I don't read warning labels and it caused damage. I would echo what RRR said and not run it until you can be relatively certain it's right.

Was this engine overhauled? Or is this just a swap? A very minor pulse could also be a misfire, or a couple swapped plugs. I'd look real close at everything just to rule out all the small things that could have you chasing your tail.