You'd want a 57 to 63 clip as 56's had squared off ends and were two folds rather than 3.
you're kind of on the right track.
55 was the last year for the 2 fold ragtop.
56 was the first year for the 3 fold ragtop and the cover itself has squared rear corners and round front corners.
57-63 are 3 fold ragtops with all rounded corners.
Do you have one without mechanism?
sorry chris, all i have is the canvas cover.
the clip & mechanism is still in the car and i dont plan on parting with it anytime soon.