Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
That makes them not 550 Lester, but the 550 sliders will fit.If the caliper mountings are K6 then the sliders are early 500 four as the 450 had the caliper braket same as early 750. Fork tubes should be slightly shorter than 750