Have you rounded up the "usual suspects" on your oil leak first? (Valve cover gasket, oil pan, oil cooler lines etc.) Oil on the driveway isn't usually head gasket unless you've got some other serious symptoms you're not mentioning. Compression drop between two adjacent cylinders, the ever popular oil in coolant, CO2 test failure for coolant, water or oil in cylinder(s)/plugs, etc. are more common signs/symptoms. It would take a fairly decent head gasket peripheral blowout to put oil out in that quantity at 70K miles.
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)