I used a kit from Novak last time I overhauled an SM420. The supplied input shaft (clutch gear) bearing had fewer balls than the one that came out. I considered using the original (from a previous overhaul) bearing as it was in good condition and had more balls and I thought it would have greater load capacity. Anyhow I used the one in the kit and so far all is well.
The fact that the bearing appears to have missing balls may not indicate a failed bearing unless there are other symptoms, like swarf in the oil, feels rough when turned by hand, etc.
