Not best, but optimum Transmission?

Guys - I bought the flexplate as shown above. I had a transmission shop do the install, as I do not have the time, space or tools to do it myself. The shop just called and said it was done, but now there's a vibration.

I haven't gone over to check it out myself yet. I literally just hung up the phone. But WTF? I'm sitting here pi$$ed off. The chosen flex plate was for an externally balanced engine. What could have gone wrong? Did I screw it up by choosing the wrong flex plate? They said it only installs one way … and they said they replaced the front seal and that the torque converter had a (balance) weight on it.

I have little to no knowledge of auto transmissions and torque converters.