Go down to NAPA and look at the trim clips they have there. And they can get more. It will be the best value you can find.
..and the nice thing is NAPA has a catalog/binder containing a physical sample of each fastener they sell, so you can see the *actual* piece of the hardware before you buy it..
Some other thoughts... Most of the fasteners may be hidden, but still..
- Are there any other local 66 or 67's you can look at?
- Do you have any friends, connections, or a car club that might have a similar car in your area?
- Track down any old salvage yards locally, see of they have any 66 - 67's kicking around.
Best,
- Art