Rear disc brakes
Swapping to rear disc brakes on a drum Salisbury axle is a bolt on, no mods needed other than to bend the brake pipe a little. The problem is the parts and the cost of them. You need, splindles, hubs, rotors, calipers, brackets, axles, drive flanges, etc. All this stuff adds up really quickly and in the end you'd likey get a cheaper set up if you can find an entire Salisbury that is already disc and install that instead, or maybe find one overseas and have someone strip it down for the parts you need. That would save some shipping costs on the heavy case and diff.
If you really want to do it we can get you all the part numbers you'll need.
I do not check PMs. Call or email if you need something.
ECR is not a parts source. We are not in the mail order business.