On the underside of the engine is what I think is an oil-return passage opening into the oil pan between the two halves. It's slot shaped and perfect for a screwdriver. When I first saw it, I thought it was put there for prying the halves apart (didn't realize it was an oil passage), so I used it. It scarred the passage some, but I doubt the machining in there matters much. I worked that hole carefully until I could get some fingers in.
My engine had been sitting for a long while, though. If your halves are better stuck together, this might not work so well.