Tiny little morsel of an update (mostly from late May)
Welding up the surplus holes in the dashboard continues.
Including slightly shrinking the size of one of the ones I'm going to keep, because it's just a bit too baggy for the warning light I want to put in it.
Not quite done yet, but better! I'm also going to end up keeping the starter button hole, and one other hole -- probably in line with the warning lights -- to put a washer pump button in.
The hazards warning light uses the extra contacts on the hazard switch -- normally used to ensure power is supplied to the indicator flasher relay for hazards use when the ignition is off -- along with a couple of diodes to prevent crossfeeding of the left and right indicators, to flash only when the hazards are on.
The other warning light -- and attendant VERY ANNOYING BUZZER -- comes on via a pair of pressure switches installed in the air system gauge feeds, so that I get audiovisual irritation when there's not enough air for the air assist/trailer brakes. I also have an additional input, in case I want to go through the trouble of adding fluid level switches to the master cylinder. Seems like a good idea to reduce the possibility of unexpected disaster.
Whether it still seems like a good idea after I have to mess about trying to find level switches, and get them set up, is a different matter entirely.
The switches are installed in a little aluminium block that I've drilled and tapped to make an air manifold out of, that I don't appear to have taken a picture of. And, conveniently, there are a pair of threaded inserts in the cab frame behind the dash, that I can use to mount it! But I didn't have any 5/16 UNC bolts, and since I'm constantly broke from having to feed the landlord's money habit (grumblegrumble) I didn't particularly feel like ordering any, so I thought I'd tap them out to M8 and use bolts that I actually have!
...
The World's Worst Tap and Die Set strikes again. The cheese-grade tap is now a bastard combination of M8 and 5/16, and I'm going to have to try remember to grab my M8 tap set from work at some point, then I can finish the job properly. 
Oh! I did manage to order in those wiper arm adapters, so I can get that done at some point. And I've got a set of wiper arms & blades in my ebay basket for later, so that I can try all of that stuff out and find out that none of it fits with the sweep I've got, or something. 