Hi Syd,
Not sure where I got the 40mm from, I just measured the one I did here and if you actually pull the king pin out and measure from the edge of the pin out 30mm and put a 10mm hole there. If you leave the king pin assembled and measure out 20mm from the bottom flat of king pin housing and drill the hole there. As for the length from memory the bolts we used were probably 25mm. I can't remember what they come up against but it does work and stops the wheels from turning too far
