kokobeach

I am looking at buying a 1977 450sel for $500.00 The body, interior and suspension is in great condition. The owner has told me that he was getting oil in the coolant. He pulled the heads, thinking it was a gasket or cracked head. I guess a Benz mechanic told him it couldnt be the heads, it has to be a cracked block. Any opinions?? Apparently, the engine was rebuilt a few years ago. could it be something simpler than a cracked block? Thank you in advance