The beams are supposed to be fitted against the frames, no mention is made of adding bearings as in this kit they are doubled, this gives adequate bearing surface. If bearings are added they should be on the inner face. I have found that using screws for these pivots leads to greater wear from the screw thread turning in the frames, pins or rivets are better.
Your unidentifiable frame spacer is in fact a scrap piece, the original drawing was modified to shorten one of the spacers, to preserve the tags this piece was left in.
Michael Edge