I'd second this. You could also go this route.
https://reverb.com/item/4056115-klu...aB0eNJSSXbmXcaAoPoEALw_wcB&gclsrc=aw.ds&pla=1
You CAN do Phase III, but there may be issues. I have a SC Ted that had the Vintage Klusons. I wanted to put Phase III's on it (can't remember if I would have had to drill new screw holes), but I could not get the old collars out of the headstock. The diameter of the PIII shafts was too big, and they wouldn't fit in the old collars. I stopped short of snapping the headstock in my attempts to get the old collars out. At the time, I found a set like Mann has, locked from the top. They were direct drop in, and work fine. I have a set with the rear mounted thumb screw on a Knaggs Kenai that work equally as good. I think I prefer the thumb screw, but a narrow margin.