Well, the fittings turned up, and I got stuck in to finishing up the plumbing (and blanking the extra ports on the manifold, because I couldn't figure out what I'd done with the idle valve); with the fuel system complete, next step was to run up the fuel pump by itself and leak-check...
First stage was with the regulator backed right off, same as I had been doing with the carb, just to see where the fuel came out. Which, to very little surprise, it did. The three elbow fittings threaded into the swirl-pot/manifold thing, which I knew I needed to seal up but hadn't done before I put the manifold on. My own worst enemy, sometimes...
Some jiggery-pokery later, I had them sealed up and the injector lines refitted. Leak check passed! Time to up the pressure...
With a great big extension cable running to where the fuel-pump relay was supposed to be, so I could run the pump and watch the pressure gauge, I kept winding the adjuster in until pressure was holding nicely at 45 psi. Expected, at any moment, that something would go pop and spray fuel everywhere but not even a drip!
The system doesn't hold pressure very well after the pump stops running, which I'm not sure is good or bad, but all the fuel stays where it should the rest of the time.
Now, it'd be irresponsible for me to go and try for a first fire-up without having my laptop to make adjustments, so, of course...
No shit, that was the first time I'd even turned the ignition on since
swapping the injection manifold in. 
Absolutely buzzing.
