Consider:
My house was built in 1959. All receptacles are three-pronged and all tested with the correct connection. I have one remaining working two-pronged receptacle in the kitchen which I would like to replace with a GFCI receptacle. The hot wire was stripped in the middle and wrapped around the screw. I assume that the power is sent down to other receptacle as downstream.
The other side has two neutral white wires and connect to each of the silver screws.
Can I cut the black wire in two, test to see which one is actually hot and connect it to GFCI LINE brass screw, and connect the other black wire into the LOAD screw?