Thanks for the guesses. You're right, he does look a little Samoyed-ish. I didn't notice that before. Oh, and he's about as big as he looks in that pic where he's standing next to the people's legs. I guess about 60lbs. You can't tell with the coat, but he's real lean.
And I did take a pic of his face where he had his ears back, and he kinda did look like a great Pyrenees.
But I don't think he has any of that in him. He's really light-boned.
ETA: I was just reading his description on FOHA's website, and it seems that he was picked up by AC after someone witnessed him being thrown from a car! Sometimes you'd never guess that there was abuse in a dog's past, a lot of them are amazingly resilient!