What engine are we talking about here, losing coolant, overheating in the past, and pressure in the system after cooling all point to head gasket... Any water in the oil?

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1987 300D Turbo 5-speed
1991 350 SD Turbo (Frankenstein)
1957 180D (Betsy)
1976 300D (best trade ever!)
1980 IH Traveller SD33T (Resting!)
1996 F-250 Powerstroke