Assuming you mean the belts with the metal faceplate glued on to them, the good news is that they seem to have been used on a few models in '66. (Although they may be less common than the basic belts that had the GM letters molded into the plastic. Personally I prefer the basic belts as they seem to survive a little better.)
At one point our sponsor TinMan (Dave) had some of these. You might want to try there...
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"So when you spot violence, or bigotry, or intolerance or fear or just garden-variety hatred or ignorance, just look it in the eye and think... The good outnumber you, and we always will." Patton Oswalt