You really have to locate the leak before determining if it is permanent damage, or just a problem. There was a small hose that was T'd into the heater hose, looped around the rear of the head, and connected to the intake manifold which could be leaking.
Using water as a coolant will promote rust, and 'freeze plugs' rust out from the inside.
If you are lucky, one rusted out, or got pushed out by ice. If not, cast iron parts may be cracked.
If fluid is coming out from inside the bell housing, you'll have to pull the transmission to determine if a freeze plug failed on the back of the block.
You have to look...
tom