There is water passage behind there. See the screw in core plug.

odds are good that it is cracked on the valley side between the lifters and deck surface, at least the last one I dealt with that froze broke there. they are not real thick on that wall.

The forbidden milkshake

https://www.ebay.com/itm/26510854465...oAAOSwbqpT8t3~

https://www.ebay.com/itm/15365994594...IAAOSw2UtczLgY

https://www.ebay.com/itm/27409395409...4AAOSw7spdyxCq

Several places to get a marine long block.

There is also an industrial long block supplier out in CA that does forged internals.

I'd very carefully look over the valley. I doubt it was just the head, though you could be luckier than I usually am.

That really sucks.

Ive seen a few frozen engines. never seen one cracked the head and NOT crack the block fwiw

If you've had water in the bottom end this long there's a good chance the bearings are shot too. I wouldn't waste the time trying to put a set of heads on it. Get it out. Tear it down. See what you really need. Otherwise you'll be throwing good money after bad.

My brother inlaw is a Matco dist in the Dallas area and one of his customers is Marine Max. He said they have 1/2 the shop full of busted froze engines, so many they are stacking them outside

I had a SBC with freeze crack a couple of inches below and parallel with the head mating surface along the outside. Not sure if BBCs crack there.

I thought for sure the blocks would of cracked in the houseboat. We didn't winterize and it does have a bilge heater but I could not for the life of me get it to come on at 35 degrees. I left a heater on in the cabin and said a prayer. Think my saving grace was the lake not freezing, the lake water insulated the aluminum hull.