I'm not going to be much help today.

Steering box. The 3 steering boxes I reused were in very good condition, The one I replaced with the rack was junk, and the Dakota has rack & pinion. I've not had any boxes rebuilt.

Upper shock mounts. I'm a welder by trade, I made my own mounts. They are pretty simple. You need an eye for the shock to mount to, and an arm that extends up and out away from the frame about 2", then a way to attach it to the frame, either weld on to or bolt to the frame at the outside edge of coil spring pocket. The shock just needs to clear everything as it moves, and the bracket needs to be strong enough to do the job. Nothing radical required, unless you intend to be going off road.... Fatman Fabrication (should show up on a Google search) makes the brackets that you weld on the frame for the shocks, and some early 50s Ford trucks used bolt on brackets the are suppose to work on these cars.

Disc brake conversion. Let me start out saying its been many years since I've done the disc brake conversions. Back then there were very few options, and most were petty costly (for me anyway). I always used www.rustyhope.com disc brake conversions. His "kits" come with a couple machined parts, a couple bolts, some instructions and a list of parts you source from whom ever you choose to deal with. His kit requires drilling and re-tapping 2 bolt holes in your spindles. These days there are disc brake conversions that use off the shelf parts that are a simple bolt on. Some even use your cars bearing hubs.
Some days we can help, some days we can't. Gene