Tadd,
The bore looks larger diameter on the rocker without the spiral grooves and it could be that this is a later roker that used to have a bronze bush, which is now missing.
Have you weighed the two rockers to see if there is much difference?
I would guess that the rocker with the strengthening web is an early rocker - 906 maybe as it looks quite like the early forged adjustable rocker in terms of this detail.
With regard to the shafts - the Tuftrided Motorsport Shaft isn't a great advance on a standard shaft but would be reasonable on rockers that didn't have a bronze bush.
If you apply DLC to a standard rocker shaft I am sure the friction will decrease and again the shaft will never wear but I would question the surface finish of the shaft and the fact it may wear the rocker.
If DLC is applied to a surface that is to rough I have been told, by a cam grider we know quite well, that it has a tendecy to flake and cause serious wear.
I have the impression that the DLC coating specialists are looking for surface finishes in the order of Ra between 20-30 nanometres but I don't know if this is true. I will try to learn more.
Can you measure the surface roughness of a rocker shaft? I have a Talysurf tucked away somewhere but it may not be accurate enough as like me it is getting a bit old and hasn't been calibrated for years
