Vibration at 2200 RPM

I guarantee the vibration didn't go away at speed, you just weren't able to hear or feel it anymore.
Continuing to run the engine out if balance can cause major damage.
You said the balancer was replaced. What's the part number from the new one?
Sounds like it's been shaking from the start, which suggests the converter probably isn't the right balance. You need to do what you can to confirm whether the balancer or flex plate has any weights or cuts for an external balance engine.
It's not going to be a cam, fuel, compression, or spark issue. I've chased vibration on small blocks before, and I kept trying to tell myself it wasn't the flywheel or balancer because I didn't want to deal with it. Once the right parts were on it was glass smooth, but damage was done and it cost me dearly.