Well, the mechanic finally drove it and got an initial impression yesterday. Right now he's focused on the torque converter, flex plate or both. He mentioned the potential of a balance issue with the engine but he's going to focus on those two first by dropping the tranny and then running the engine.

He did put his timing light on it and noticed the car was off by a tiny amount so he reset it to the mark where it was initially set when the engine was rebuilt.

Will probably have to wait another week or two before he can dive into it more.