Hello All,
I went through this about 10 years ago when I replaced the hacked PS setup that that the PO cobbled together. Starting at the steering column, I bought some 2" delrin rod and had it turned down so it JUST squeezed into the end of the steering column tube. Cut it to about 3" or 4" long and had the appropriate hole bored through the center (3/4" IIRC) to form the bearing at the firewall end of the column. Cross drilled the piece and installed a grease zert in the column tube for lube. Super solid and smooth. I also cut the steering shaft back so only about 1.5" protruded from the column and had the flats machined in it to form the Double D that the steering joints use.
To work out the basic angles and rod lengths I bought some 3/4" wood doweling, and rubber tubing that just slipped over it to simulate the joints. Since the single joints have a max working angle of about 35 degrees each, I used an angle finder to keep me in line. I could move the wood dowels around to show me clearances in various routings. It made it real easy to visualize the setup before I bought even one piece of hardware. With the 3 joints, I had to use a rod end to support the rod running down to the box, and it helped me place where that went, even using existing threaded holes in the frame.
For the box I bought a mount plate from BTB, and sourced the appropriate unit (late 60s Chevelle if memory serves) from a local classic car wrecking yard. Cut off the old home made plate and installed the new one as close to the crossmember as I could get it. I've also seen installs where the box was sticking into the hole on the frame, but I just got it tight. I didn't use a spud shaft, but assembled the box, joint, and long piece of steering rod outside the rig, fed it through the hole from the front, and then bolted the box to the frame. The joint lives inside the crossmember, but I can still see it, and somewhat get to it through one of the holes in the frame. If any of the other joints give me reason to worry, I'll probably unbolt the box and inspect, but they are all solid and will serve me for a long time.
I didn't install a slip joint, but at some point I will flex it hard and see what kind of movement I have.
I know I've probably missed a few points, and I can take some detailed pics of my install (as well as a shot of the delrin bushing I had made a an extra), just let me know.
. Gonna be a little slow going as I am on a budget, but I'm sure we will both be learning a lot along the way...
It was soon rectified with grade 8 bolts. You'll also notice the wire wrapped around the cross-member, it held the radiator mount in place. 
