Aforementioned material arrived, and it's almost all correct!
Apparently, though, I decided to order a piece of 1/2" tube to make
the port on the air-box for the air compressor's inlet, when I
should've ordered 1". Guess I've just got myself a new lightweight
racing peashooter. 
An air-filter has been ordered, along with a filter housing lid, so I can get everything sized for it to fit properly. I'm also waiting on some fittings for the fuel filter and the pressure regulator, that are making their way through the postal system.
If I survive work tomorrow, and remember to bring my drill, I'm going to make a start on the injector hold-downs. Maybe I'll even finish up the manifold welding (reinforcing pad for the idle-air valve fitting, dress-up pieces on top, and whatnot) and do a bit of clean-up work. I'd really like to get the manifold to the point I can call it finished, and ready to go on once the supporting stuff is there. (Leaving the carb on for as long as possible, so the truck's still mobile-ish until the changeover point.)
May also pick away at the roof a bit more, too. There's plenty to get
on with, I just need to work up the energy and will to do it. :D The
good news is, my joint pain seems to be subsiding for the most part,
which is a tremendous help! I just need the empty bank account to heal
itself, now... And to magically gain several more hours in the day to
do stuff... 
I do have some video from the manifold welding that I need to get edited up, too; it's not the most exciting stuff, but heyho
The Following Day
Three of them! 
And it looks like they'll work, despite not everything being lined up perfectly. (Which is why I decided to go this route, with effectively individual injectors, rather than a single solid fuel rail; much more tolerant of my wobbly work!)
Additional fettling required to clear the plug, though.
Then cue another hour and a half, trimming the ends of the injector bungs to length and dressing them in with the runner walls.
(Clearly obvious that I didn't get 100% penetration on the segments of the runners, particularly early on in the process. It'll either be fine, or it won't. (And if I have to make a 2nd version of the manifold, with the lessons learned from making this one, so be it.))
One of the injectors is going to be interesting to get the hardline to, due to not having as much clearance to the plenum, but I'm still confident I can make it.
At close of play, that leaves us at this point!
Didn't end up breaking the welder out, though. That whole process took
quite some time -- far longer than expected -- and I decided I'd
rather head home and put the kettle on, by the time I was done.
I did, however, manage to wriggle my way in and free off the adjusters on the 4-way valve, so I know I can tweak now; and I've had fittings turn up for my fuel filter, so I'm getting closer and closer to having everything come together!