Don't disconnect the yellow wire under the dash. No need. Disconnect the battery, wait about 30 minutes then remove the airbag. When you unbolt the bag, lift up gently. Then you will see a little yellow wire in the center of the bag. Pop it off. Sometimes it is easier to just lightly pry it off with a small screwdriver. It's a button cap type connector. The car should have two small square horn contacts. Those contacts are very problematic. Might not be the harness that goes down the column.
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018