Virginiafiretruck, he may not have the same setup in his 59 as we do in our AD trucks.
I've clearly seen the vacuum switch bolted to the side of the tranny..
Where is your two speed axle switch mounted? Do you have any pictures of it? The adapter is likely not far away from this vacuum valve.
A truck with a factory installed two speed would have come with an adapter, did your truck come new with a two speed?
Grigg