So, I'm kind of curious of what this is.
Fill it back up on a slab of concrete and let it run. if it start to show a leak to the back of the block. find and repair as necessary.
Now, I will say this. When I was working a while ago out of town and driving my 94 civic, I found it had a blown head gasket. but wasnt mixing oil with water or water with oil. No, my HG was leaking right into the cylinder or cylinders. Later it got so bad, that when I shut the car of and let it sit, it would leak over night into the cyl. In the morning I would have to sit there and let it start up then sit there and make it run, by just dumping fuel into it and forcing most of the water out and the rest dry out with the combustion.
so, head gasket is still a possibility, IF nothing else is showing up at all. Do you have a heater core hooked up? there have been times where a heater core goes bad and it leaks right there in the fire wall. so check for everything