67 is wired slightly different than the 68. An orange wire leaves the fuse box and goes to the light switch and from there goes to the brake light switch.
You have power leaving the brake light switch so the problem is downstream from there. Check the signal light switch connector on the steering column, where the white wire from the brake light switch connects, should have 12 volts when the brake pedal is depressed. If you have power going to the signal light switch when the brake pedal is depressed and no power going to the brake lamps, yet have power going to the lamps when the signal lights are switched on, I'd say you have an inoperative signal light switch.

Unless the brake light switch is not adjusted correctly to the pedal and the switch is not closing when the pedal is depressed.