[punyXpress]

Most of the bearings have inner & outer sleeves & the method of getting grease in between them may be a problem.
A system where bolts are bored & tapped for nipples could get grease to the inside of the inner ' race ' then a notch ground into the edge surface of the inner woulg allow grease onto the needles, but could this maintain strength in what is often a highly stressed ares?
The drilled bolts would save castings being modified.
You can tell from the above I am no engineer!