Neatened up the wire looms, tested the rev limiter (good) and started adjusting the spark table.
Took the car for a ride the other day to stress test it and listen for pinging, and heard none, but the brake pedal was going too deep so I rolled home.
Got a chance finally today to bleed the brakes: fair amount of air came out the passenger rear, and that brought up the pedal pretty well. No leaks detected anywhere though so I'm looking around for where the air got in.
I did spot a possible drop on that front sender switch so I tightened it an eighth turn. 
Thinking the brake bias adjuster might be the culprit. We got the bubbles after my assistant turned the knob on that thing.
I plumbed it in years ago just because it came with the other parts I got. Was a bit of a thing too, since the threads in its ports don't match what VW Bug brake lines come with. I had to flare on the new connections myself, and was right surprised when they worked without dripping.
Still no sign of a drip from the device, or either of the connections.
I'll be a bit miffed if the part itself turns out to be NG. Though that would be pretty on-brand for this build.