Mordrop, or however they spell it, does still exist, and I believe there is another company that makes dropped axles. You might check into those.
Disk brakes are a real good idea, and you might want to look for a 1/2-ton axle to drop to make it easier to convert to disks.
The disk conversions I've seen would all put Chevy 5 x 4.75 hubs on the front, so you might want to look for a rear axle from a GM product that would have the same pattern.
I don't see the suspension changes you're talking about as radical. Z'ing the frame is a different story, but I don't know anything about that...
