[antonye]

Those calipers won't fit your forks as they are 65mm mount and your forks take 40mm calipers (the distance between the bolt holes to mount calipers to the forks)

I've got a 916 master cylinder with resevoir for sale - you'll need one of these to push more fluid down the lines if you switch to twin calipers.

All you'll need then is another caliper, another brake line and a twin-line banjo bolt for the master cylinder.