[b-man]

It’s just machine work.

It takes some figuring where to drill your new bolt pattern so you don’t run into obstacles like stiffening ribs inside the front hubs or on the rear axle flanges avoiding those big holes used to access the bearing retainer bolts.

Some examples of what you have to deal with when doing something along these lines pictured below.

The front rotors started out 5 on 112mm and were drilled 5 on 4.75” GM intermediate. Rear drums started out 4 on 130mm and ended up the same as the fronts, 5 on 4.75” (120.65mm). One of the holes had to be plugged on the rear drum because no matter where you tried to place the new 5 bolt pattern one would always interfere with that hole.

All the machine work was done at my workplace in our machine shop as a favor by one of my coworkers, I just had to figure out how to get it the way I needed it to be.