Mark- I've got '57 5700 with 2 speed rear axle. Unfortunately I also inherited the brake and hi/lo shift problems. Fortunately I've got the problems mostly sorted out. I'd imagine your 2 speed axle has a diaphram on the rear axle that is activated when the knob is pulled by placing vacuum on the diaphram causing the axle to shift. Also the brakes are a hydrovac system. What you saw the vacuum hose going to was not the master cyclinder but rather a Bendix Hydrovac. Most likely you have a vacuum leak somewhere and also the hydrovac as well as the 2 speed rear shifting mechanism are probably stuck from years of nonuse and need some TLC to get working properly. To start it may not hurt to bleed the brakes, hyrdovac and mastercylinder to make sure you've got fluid everywhere. There is some info on the net and a lot of good archives here that have helped me.