Brad is correct, the original posts on the regulator were
solid and just slid in the channel with a lubricated leather
washer on either side of the channel. They were greased and
worked just fine for the life of the truck. That life was not
meant to be 65 years either. A roller may have lasted longer,
but would have added more cost to the assembly and GM cut
corners every place they could.
The replacement rollers from the vendors are cheap and work
just fine. The problem you will probably encounter with them
is the hollow rivet on the post will most likely split when
you try to swage it.
The posts that I fabricated were made using a low alloy
annealed 1020 CRS and the hollow rivet formed head looks
just like the original factory one.
http://www.pbase.com/dennygraham/image/120007831dg
It would be helpful to know the year of truck in question.