Engine cant separate from the transmission

Have you removed the starter. Sometimes people don't and it gets hung up on it. Just look around the area where the engine meets the transmission and look for anything that you might need to remove that could keep the tranmission from moving away from the engine. Even an engine mount bracket could be the culprit.
Let me know some more and I will help.
You also have to keep the engine and transmission square or inline with each other as you pull them aprat. Sometimes to get them started coming apart takes a pry bar on the engine or the transmission. There is genreally a little tab on wither to pry against for this purpose on the lip of either the engine or tranmission where they meet.