Okay, I fail to understand.

Formerly, the 2-wire cord was connected to pins 2 and 4 of the Yaesu
connector. These I assume correspond to the +hot and -hot of the 120V
input winding to the step up transformer, leaving the ground floating.
I looked at my 3-wire cord and determined that my hot wires were the
black and white ones for the 3-wire cord, and that neutral (chassis
ground) was green. So I connected wall ground through ground line of
the cord to chassis ground pin of the plug, leaving the hot connections
unchanged.

Is there something I should be doing different?

Thanks,

The Eternal Squire