Tapped the thermostat housing for the temp sensor for the EFI! Took over a week, because the first tap I used just broke off with little to no effort or warning. 
Fine, be that way.
New tap was ordered from a trusted supplier, and after a few days I could finish that off.
Loosely assembled, waiting on heater hose for that little link stub that goes down to the top of the water-pump, which I now have.
Headers coming together bit by bit:
Currently stalled on that because it turns out the 6 meters of 38mm
stainless tube I bought ages back, which has been stood up against the
wall in the unit in the packing material, was in fact 30mm
diameter. Not sure if that was my screw-up, or their screw-up, but it
makes no difference at this point.
Thankfully, I think I only need another meter or so of 38mm, so I've ordered that so that I can finish the damn header. The 30mm? Not sure what I'm going to do with it, but I'll find something...
Once I get the merge and 90 done, I think my next step is probably some flanges (probably V-band, honestly), and make up an unequal-length Y to merge the exhaust and bring it about level with the bellhousing in such a way that I either avoid blocking access to the oil filter housing or if that's unavoidable then at least the offending section is easily removable as needed.
It would still somewhat suck to have to remove a section of the
exhaust to drop the oil filter, but it would suck even more if I did a
Subuwu and gave myself a ring of fire to wrestle the filter out
from... 
Oh! And I have potentially got a solution in the works for the wiper
spindles; I just have to get some time on the lathe at work for some
hole-drilling so that it's all concentric. Y'know, because wiper
spindles are really a big priority when I still have the cab corner
all in bits. 
Still no change on the starter, so I'm no closer to firing it up yet. In fact, I think I went backwards because I have to re-do the coilpack mount because it runs right into the dipstick...
In the meantime!
Can ya tell what it is yet?
That's right! It's a ...n unfinished widget, because my brother borrowed the drill from the unit, and I forgot to grab mine from work.
Oh, right, yes, sorry, it's a cable tube; to neatly (hopefully...) run wires from the starter solenoid nad whatnot, behind the headers and protect them (hopefully...) from the heat a bit. It does occurr to me that I might not actually have all that many wires to run through there and it will be a little silly if there's only one, but look, that's not the point and I've already made it now.
...
Anyway, my replacement exhaust tube has arrived and looks to be the right size, so that's something else I have no more excuse to put off (but will anyway.)