Are you going to make the axle?
If so, you want a plain 20mm cylinder with a flange on one end and female threads in the other, into which you screw what is in effect a detachable flange. You can be tarty about rebating the axle clamps on the end of the fork to hide the flange if you like, although it's not essential.
If you buy this, it says it fits all Marzocchi 20mm forks, so if that's true I can let you know the dimensions of the fork ends on my Shiver SC for reference.
Are you going to make the axle?
If so, you want a plain 20mm cylinder with a flange on one end and female threads in the other, into which you screw what is in effect a detachable flange. You can be tarty about rebating the axle clamps on the end of the fork to hide the flange if you like, although it's not essential.
If you buy this, it says it fits all Marzocchi 20mm forks, so if that's true I can let you know the dimensions of the fork ends on my Shiver SC for reference.