It changes the double chain to a stronger single chain in addition to changing the drive/driven sprocket ratio inside the trans.
This sprocket ratio multiplied by your your diff'* final drive resluts in your trans' FDR.
If you have an SE, you have a 35/35 gear set and a 3.05 differential.
If you got a 37/33 gear set and kept your 3.05 differential, you would have a 3.42 FDR.
The gear ratios in ZZPs site are assuming you have a 3.29 ratio diff..
If your after a 3.29 FDR, all you would have to do is swap out the diff and sun gear.
ZZPs kit can only be installed during a teardown/overhaul but the diff can be swapped relatively easily.