2003 Chrysler PT Cruiser Engine oil and Antifreeze mixing t

I bought one engine at a salvage yard. The first one was cracked under the oil pan. Salvage yard replaced it. The second one started mixing oil and Antifreeze together. Now I am stuck with that engine as the salvage will NOT change it. Can this be repaired? The heat tab are still in tacked on the engine. Salvage yard says that I overheated it.I differ with him as I pulled over and turned the engine off when the needle started to rise. It did not get passed the 3/4 mark from mid-range. The BBB and BAR says that if I did overheated the engine that the heat tabs that the salvage yard put on the engine would have fallen off the engine. Where do I go from here. I am retired Military with a Mom who is blind, a child with cerebral palsy. Need help. Thanks