The fork pistons on the FZR600 are about 2" longer than the fork pistons on the Seca II fork:

The damper rods on the FZR600 are about 1/2" shorter than the damper rods on the Seca II fork. Both damper rods have the same size and number of holes:

The FZR600 springs are shorter than the Seca II springs and the FZR spacers are longer than the Seca II spacers. The combined length of the FZR600 spring/spacer is longer than the Seca II spring/spacer (the FZR spring is on bottom; the stock Seca II spring is in the middle):
