I'll toss my $.02 in.
These disk brake conversions are shyt for these trucks. You will lose any reliable service brake function. Sometimes it will hold, most of the time it will not. The best is when you think it will hold walk back to hook a trailer up and the truck starts creeping away or even better starts creeping towards the gooseneck and your tailgate is still up. Braking is not any better than a properly adjusted drum setup. If you are towing heavy the rear disks can not take the abuse. Disks do not have the mass to absorb the heat and can quickly rise in temperature with little to no warning yielding zero brake efficiency. Disks may be able to dissipate heat faster, but they also heat up much faster. The mass is the equivalent to your tank on an air compressor. You need a location to store energy until it can be released.
I tried one of these conversions. Ran it for a few months before removing it. Went back to drums, 1 ton cylinders, new top of the line Wagner shoes, new spring hardware, braided lines, removed the rear weight sensing proportioning valve (didn't have the fittings to work with the braided lines), and tuned up the star wheel with a triangle file. I never had an issue with the drum brakes since then (5-6 years). I've never had to manually adjust them either.
If I had a hard on for disk brakes it would be an axle swap. Otherwise I would make sure the drum brakes were setup for success. I have little doubt the muddy roads I have to drive on would chew a set of those unprotected disk brake conversions up in short order since they don't have shields.