12 bolt rear end - brake question

[83burban]

This is what I have gathered,

The axle has 3" diameter tubes which then neck down in the last 1" or so. The backing plate is then pressed onto this necked down portion. I am going to run Ruff-Stuffs weld on mounts for it, but it just seen weird that there are no flanges.

Will this cause problems for me when I am ordering new bearings and such, or are all the bearings for 12 bolts the same?

What part number rotor should I be using for this. If no one has one offhand then I will just go the parts store and look for one that will fit the bill.

Thanks