Bitter taste of defeat! So much coolant in the oil pan.

I would guess you disturbed the gasket on the timing cover when trying to deal with the oil pan being already installed. If the water passages didnt seat to block, it would pour straight into pan. If you tore gasket around block passages on timing cover it would do that. That would explain the water level in rad being even with top of cover, lower than intake passages.Is it possible you broke timing cover? Of course, this is just a guess without pics or more info.
You are going to need to flush block out so you can get as much gunk out as possible, fill it up with oil but hold on the water. Then do a comp test to see if its got head gasket issues or cracked head. That should narrow it down for you.