Converter will no go in all the way

Had 727 rebuilt, using same converter that came out of it. This is a high stall racing converter, but I've had it in and out of this transmission several times for engine rebuilds and I've never had to wrestle with this thing before like this!
BTW the tranny is out of the car on the bench.
I've rotated the converter, rocked it side to side as I rotate, pull out slightly as I rotate, pulled up on it as I rotate..
Anybody have a trick to getting these things to go in all the way?
I've been fighting this thing for about an hour now.