I never gave the chrome trim pieces on front seats much thought until I installed a new interior on a 300J.
I learned there was more to it than I would have guessed. I made this summary of the lower trim pieces and the upper seat back pieces.

1960 - 1961
The lower seat trim pieces are unique to these years because of the swivel latch.

The front seat back pieces are diecast and have a "channel" on the rear side. Each front seat gets a right and a left piece. Right and left pieces will not interchange with each other. These pieces are used 1960 61 62 and on some early 63s.

1962

The swivel is gone by 1962 and the lower seat pieces are unique to this year. They are a diecast piece and do not interchange side to side.

The 1962 front seat back upper chrome pieces are the same as 60 - 61.

1963

The lower seat pieces are new this year. They are a rectangular stamping which will fit either the driver or passenger seat.

For the front seat upper pieces, it looks like early production cars (November 1962) used the 60-62 die cast piece. Most Js used a new style piece which was a rectangular stamping of similar design to the lower piece. The new style piece will fit either side of the seat.

1964

The lower seat piece for the driver side is the same as 1963 but the passenger side piece is new this year. That piece was re-designed for the reclining mechanism that was used on the passenger seat.

There were no trim pieces for the front seat backs. The K went to a metal piece replacing the previous carpeted seat back.

1965

The lower seat piece for the driver side is the same as 1964 but the passenger side piece is once again new this year. That piece was re-designed to allow for the rear toe release in the reclining mechanism.

There were no trim pieces for the front seat backs. The L continued with the metal seat back in place of the carpeted piece.