My shop is 400 yards from the house, and weather is nasty here, so no measurements, but I had your problem last week.
I rechromed a perfect grab bar, for my son’s K3. When I went to fit it, the stems were too narrow for the rubber grommet that fit the bar (centres were to close together). Turns out the K5 and K6 with the bigger “frying pan” turn signals have a larger diameter shank and stem, AND the dowel for the wires and the screw hole are further apart....... also, the base plate welded to the bar is larger on the K5-6.
Most important, I mentioned it here and one of the other Members swapped me an earlier one for mine! Worked out fine.