bcgmc,
The valve on the transmission was the vacuum 2-speed rear control valve. The valve had a push/pull cable that went up to the gear shift knob for high/low selection. The vacuum lines attached to the valve went to the rear (Hi & Lo), vacuum supply up to the fire wall and a small line up to the speedometer adaptor. Do you still have a 2-speed rear?
The steel vacuum lines on the fire wall looks like it could be the fresh air filter for the Hydrovac. Is it attached to what looks like a valve cover breather cap mounted inside the cab?
The other lines on the fire wall are the vacuum lines, check valves to prevent backfires from blowing the vacuum lines up etc. You could have a large vacuum tank mounted on the frame as well.
The large cannister on the frame is most likely the original Hydrovac (brake booster) that was abandoned when they install the modern dual pot MC with it's booster attached.
Hope this helps,
Mike B
