I know of a good frame out of a 1968 Parisienne convertible on the west coast. Probably a little different than 66?

65-66 frames are the same, 67-68 the same, an 69-70 are the same. 65-66 frames are unique as the idler arm positioning is quite different than 67-68 & 69-70. The convertible frames are 1" wider beneath the doors.

Generally the frames are all the same, but things like frame horns may differ from 65-66 to 67-68 to 69-70.

A few years ago I needed a frame for my 70 Parisienne, and as usual things aren't available when you need them. I called everyone I could think of that had a 70, and they'd all scrapped their cars. I ended up travelling about 8 hours to Saskatchewan to get a 69 2+2. I parted out the car, and kept the frame.

so I should stick with a 65/66 frame then? Also, silly question, is the frame similar to a Chevy frame or American Catalina/ Grand Prix frame if I am looking in the US for one?

I think the Chevy frame works but for sure the American one does NOT fit, it's completely different.