Crank end play, destroyed converter, 408 nightmare

I have a friend that I believe didn't properly seat converter. I'm going to insist we jack up and crawl under. Unbolt converter. And reseat. I'm assuming 727 is like any trans? If seated should spin gears. If not? You would know by sound and inconsistent spin?
If the converter isn't seated and the trans to engine bolts are pulled up most likely the pump and/or pump gears will be destroyed. You generally don't get a second chance at this