What you'll need:

• 06-08 R6 shock (earlier years WON'T work without alot more work)
• Spacers
• Dog bones
• I also recommend a heavier spring for the fzr600, around a 650-750lbs, the stock r6(~500lbs) is perfect for the fzr400.
  

The Shock:
These can be picked up of eBay for next to nothing ~$25.00USD.

:!:You will need to round the lower shock mount so that it clears the suspension knuckle.

All of the R6 shocks that can be used for this conversion look like this

This image dipicts were you'll have to grind the shock slightly so it clears the knuckle.

The spacers:
You need two of these spacers as the FZR shock is 10mm wider than the R6 and uses a 12mm bolt as opposed to a 10mm bolts.[ 10mm dia hole drilled through]. The green section needs to be 5mm wide, diameter doesn't really matter and can be anywhere from 14mm to 20mm. The red section should be just under 12mm dia and ~7mm long. For the FZR400 ignore the stepped down section on the left(red) as the FZR400 uses a 10mm bolt which is the same size as the R6, so you only need the green section.

This is where they go

Dog bones:
~10mm short than the FZR dog bones, this raises the bike back near stock. 6mm thick.

Stock on the left next to two new ones

For the fzr400(3en1) I had to grind a tiny amount of the top frame mount although I didn't have an issue with the 600.

-Dru86