What are the symptoms of a bad torque converter?

I recently got my 360 going in my dart and I've started to drive it around a bit. No issues with the motor whatsoever. But my problem is that it doesn't seem to takeoff from standing very good. Once it gets some speed it's pretty good though. I haven't really womped on it completely yet considering it's a new motor but I still feel it should have more getup.

The trans is a 999 with a tf2 shift kit in it, and unfortunately it is a lockup, but I used it because it was in good shape and has the low first gear set. I'm using the converter that was with the trans, which may have been a mistake...

I'm running a 360 with a comp xe268h, eddy heads, KB 107 pistons, Weiand intake, Holley 650 ect, it should have more go from a stop than it has, it runs strong, so the motor isn't the issue.

I have 2.92 gears in the rear so that doesn't help either. From a stop it feels like the rpms don't match the speed, the motor revs and the trans slowly accelerates and then has the go it should.

What are the symptoms that would indicate a bad converter? And is it even worth it to get a lockup converter?