The shaft needs to be a true .8750 dia (can't recall tolerances) with a hardness in the upper 50's/lower 60's. The reason is to distribute the load evenly to all the needles (no slop) and the hardness is needed to prevent the rollers from digging into the shaft.

I found out all this info after the needles in my 440S rockers let go. Stock OEM style shafts were supplied in my kit.

To the OP: Remember....cheap parts cost less up front, but twice as much when they fail and even more to clean up the mess. Don't skimp on the rockers.