EDIT: I just checked and it looks like you've got those large knobs. You might just have to get one and see if it'll work. Sorry to not be of more assistance.
Is this a picture of your radio and knobs? If so, I don't think you're going to get any more clearance than that. At least with that radio you won't need the space to insert CDs or anything. If they were the same as those in SC... They were really quite large.
Another thing to consider is that your fog lamp knob is illuminated and I don't know if just changing the knob is even possible.
This picture shows my 1987 radio and knobs. I don't believe they are different size than your picture. However, my cigarette lighter is from a 964 to replace mine that was lost. If you look closely you might notice that it is actually slightly larger than the fog light knobs. This suggests that the 964 knobs will be the same size as your picture.
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