Im busy replacing mine rear wheel bearing also on my Skyline R34 GTT. I got the parts 43281-AA100 for the left side and 43280-AA100 for the right, and as u said its larger, but not a big difference.
I think maybe the wheel bearing assembly hub got smaller cause its been pressed with the old one. Maybe if you get a new one it would be the same size as the wheel bearing,
Maybe im thinking too far or going crazy here... . Im also been searching around for answers. Might even order a new hub to see if it might work.