Oh one other thing. Do you have any history about the car? We were talking about heads and head gaskets but it could also be a cracked block. If it was ever in cold enough weather without antifreeze, freezing could have cracked a cylinder wall in the water jacket, that is about the thinnest place of metal and if a freeze got it, that is a possibility. That is what you want to check before spending money on head jobs and such.
It’s been a Texas car all along, so I doubt it has seen temps below the teens. I’m not sure how to check the ownership chain.