How is reverse?
I'm thinking you might have a valve body problem, or a exploded planetary set.
Betcha (Tracy) fishey68 would know for sure where to look.
I think your on to something Greg. Could very well be an exploded and seized up planetary. I'd drop the pan and see if there's any shrapnel in it. If no shrapnel in the pan they probably screwed up the shift kit installation so it might be best to just find a different valve body and start from scratch