So here's how I ran the system:
3/8" brake line from the intake midway back down the frame. Then I used an old fire extinguisher bottle as a vacuum canister. I tied in a Tee back to the rear crossmember, just before the axle. On the axle I mounted the electric solenoid, so there would be the largest vacuum signal to feed it. A short hose jumpered from a short piece of tubing in the solenoid to the axle. The solenoid was powered from a spare fuse at the panel, switch mounted at the shift knob. The solenoid works instantly, the shift happens in the time you lazily push in the clutch and release it. I'm not even sure if you need to push in the clutch to shift?
My speedometer doesn't work, so I didn't bother reattaching the (leaking) vacuum line to accommodate for the shifts. Some day when I work on that, I'll investigate further.
