Car looks great!
Those vinyl top drip gutter retainer strips were stainless steel in 63 - 66. Then in 67, depending on the assembly plant and the time frame, they were either black plastic, or clear plastic with an embedded mylar chrome strip.
The stainless strips are indeed very hard to remove without destroying them. I've been successful a few times, but you need to plan on about 2 hours per side to get it done!!
The mylar 67 version shows up on eBay fairly frequently. It is not "correct" for a 65 or 66, but lots of people use them as a substitute for the original stainless strips.
Here's a set on eBay now:
https://www.ebay.com/itm/19572653927...Bk9SR7jOyI74Yg