There may be a little slot on the underside of the knob. Use a tiny screwdriver to push up on the little clip that holds it in place.
Got a close up of the knob in question?
Pull like hell, they are a press fit, you can use pliers, but try not to mar them, or a small block of wood, and a flat screwdriver in behind, tehy pull straight off the shafts, hope that helps,
the whole heater control assembly unbolts with 4 speed nuts from behind.
On a 67, you are best to remove dash pad, easy, 2 nuts and some screws, drop the column, then unscrew the entire dash cluster and let it hang, dont forget the one hidden screw for a bracket behind the steering colunm, easy to see when the column is dropped.
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Beaumontguru
MY BEAUMONT HAS 4 STUDDED TIRES AND 2 BLOCKHEATERS......AND LOTS OF OIL UNDERNEATH. The other one has a longer roof.
thx guys stuck little screwdriver underneath knob pulled like hell got one off so far will try other tomorrow also thx for info on dropping steering column must easier