I forgot to mention that the threads are 3/8 X 24. I have three of those slave cylinders and the 3/8 X 24 die I had wouldn't thread on the spare one so I bought a new one thinking it was miss-marked or the stud was metric not US standard. Also watch for the markings showing which side is to be run on first, it does make a difference. One side starts the cut more shallow and the other end cuts to the finish depth in case you haven't done this before.
It turned out that the first of the threads on the spart cylinder had a problem.
I threaded the new die on the stud of the cylinder I had been using and ran it up to the top of the threaded area. I then put the two nuts on, ran them up a bit short of the die then locked them together. I then put the bottom nut in my vice and tightened it up then with a 1" open end wrench I started to run the nut up the shank cutting threads as I went. I later swithed to a 1" box end wrench which was longer and didn't have the open end for the wrench to slide off with.
Previously; I had marked where I thought the threads should end by matching it up to wht mounts plus allowing for the upper jam nut to be installed then stopped cutting threads there. After backing the bolts and tap off I run one of the jam bolts all the way up and holding the clutch arm all the way to the rear I tried to install the slave into the arm and the pivot. I ended up doing this three or four times before I got it correct. It is easier to cut more than remove cut threads.
Things of note: I think the slave and pedal assembly might be LR but I have had them so long I am not positive. By the looks of them and others I have seen from other compnies, if they aren't from the same source they sure look like they should be just with different decals or company logos impressed into the body.
The other thing of note was that during the cutting of the threads I alternately got easy to cut then in places it took a lot of arm work to get the cutting to climb the stud so the temper probably isn't the best you could want.
Don't forget to use cutting fluid to make things a bit easier and to give life to the die.
For what it is worth...
Lee