I think the issue is the exact size of your 1968.
There are 2 sizes ....one is a 3/4" with 50 teeth on the spline. The 68 - 69
wheels have a 5/8" bore and 36 teeth.
The larger one was used 1965/66/67 only.
I am sure someone will jump in and correct me if thats wrong.
Mike's question about the dash is important also.
I have seen your website and know you have a steel dash, correct?
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