Wheel Hub Differences

Are there any differences between a drum brake D30 hub, a D27 and a D25 hub? I have a set of D25 hubs that are machined for a disc to be mounted to the backside. From what I can see, everything looks the same including the bearings. I am upgrading the NT D30 to disc with GM calipers on my 3A.

 

I used d25 hubs on a d30 drum axle.

 

The bearings are the same but you may find as I did that the hub mounts a little far out onto the end of the spindle. I discovered there are 3 different bearing races of different widths that can be used. I had to find the correct one so the spindle nut threaded on correctly for proper thread engagement. I noted this in Focker's "Front Disc Brake Tutorial" page 2 of the thread.

Front Disc Brake Tutorial | Page 2 | ECJ5 (earlycj5.com)

 

Be cautious here.
There are diameter differences on the wheel bearings.
Generally speaking, the D25 bearings are smaller in outside diameter, as is the wheel seal for a D25 hub.
Some of the D27 wheel bearings will be the same as the D30 for drum brakes, larger in diameter.
There was a change by serial number in the production change of the hub/bearing diameters.
Spindle diameter (where the wheel bearings ride) will be the same for drum brakes.
Of course there are obvious differences in spindles as far as spindle bushings vs bearings are concerned.