The snout can hang in the tail of the crankshaft due to rust or debris. You should be able to back the converter off about 1/8". Otherwise, it'll stay with the engine when you separate the trans. That will create a huge spill, at least. If you can't get it free, then make/use some guide pins to be sure the trans slides straight back from the engine to prevent pump damage, and place a big wide pan or a LOT of absorbent material on the floor to catch a couple quarts of trans fluid.