I had mine converted to a signle front disk for a local rally , the easy way.
It DOESN'T work!
What we did was the obvious.We just took out the right caliper and used its screw on the left for the cable to connect.
The pump is very strong , as it is designed for operating with 2 brakes , and braking on loose surfaces has now become an act of balance and precision. Squeeze it a bit much and you loose it , don't squeeze it and you never stop!
What I suggest is using both front calipers.
Look here: www.ktm-sommer.de
These guys have a high front fender conversion for the 640.
As far as fork guards and the rest is conserned:
I used fork-guards designed for Husqvarna, the 640 Enduro guads were not even close to mounting on the forks, even if modified somehow. The holes point to comletely different directions. I do not know about the SX models' suspension.
The front fender is a 2 piece Acerbis universal (orange + black ) which was simply bolted below the "bridge" provided.
I'll post photos later.