yes theere should be a safety switch on the clutch pedal to where it wont start without the pedal pushed in
first figure out why the pedal wont go in and once thats moving try starting with the key and clutch working
if that isnt it and jumping the solenoid works then replace the solenoid.
there were two different engine options for your bus so you need to figure out which one you have before we can help you figure out your wire harness but in that era the electrical is pretty straight forward simple.
after you get it turning over the next thing will be cleaning the points and a temporary fuel source because the tank is probably trashed.
i have rescued many old vehicles just by strapping a five gallon can under the hood for the fuel pump to feed off of.