Just bought a house, 70 years old, want to upgrade 2 prong outlets
I would not put a 3-socket outlet on a 2-socket system, even though a lot of electricians do it. The neutral and ground are not the same thing. Neutral is part of the circuit and has electricity flowing through it. Ground does not have electricity flowing through it, unless there is a short. There is already a topic on why you should not connect the ground and the neutral.

If you think you can guarantee an earth ground, then hook it up and test it like this:

(1) hot and neutral CORRECT VOLTAGE

(2) hot and ground CORRECT VOLTAGE

(3) neutral and ground NO CONTINUITY

The outlet should pass all three tests. In other words if you put a connectivity tester on the neutral and ground sockets it should NOT beep. If you put the continuity tester between the neutral and the ground and it throws a huge spark and melts, then you just found out you did something wrong.