Looking for the hinged portion of the fold down seat.
As has been stated, if this is what you are seeking, I hope you don't intend to rechrome it. A long piano hinge (its generic world-wide name)
will not rechrome well because of its construction and the long hinge pin. I bought a 66 kit for the hinge and put the rest of the pieces on the shelf. All the original remaining pieces from my 66 Fastback, plus the front piece from a 65 curved section (early 65 Fastbacks use different bumpers and that front curved piece does not have the bumper mounting holes) to my chrome plater. The reproduction piece is not marked. (For reference, to rechrome that piece is about $80-90. To remove the hinge pin, strip the old chrome, triple chrome plate the two sides and reassemble the hinge will cost was $350-400.
The "kit" itself is generic for 65-68, and you will wind up with a 67-68 left side latch section to use on a 65-66 Fastbacks that do not have a left side latch.
Jim
Jim