The problem is more involved when dealing with a console in the 68 (67 too I believe). The upright section of the console has a padded cover (similar to a dash material) that goes over the radio opening. The 2 radio potentiometers protrude through the padded piece, which also addes to the depth which the knobs require in order to mount onto the shaft. The stock aftermarket radio knobs do not work properly. I have this same problem, but haven't bothered to do anything about it since the 2 outer knobs which control the tuner and volume work fine. It's the inner knobs which control the balance and treble/bass that won't work. I just set these and leave them, so I have been able to live with it. You could try contacting Custom Autosound, they probably make the right knobs. Also, if you can get your hands on the original radio knobs for a console car, those would work too.