There is a little bit more to the vacuum lines in T birds and I assume Fords of the same vintage. The source of the vacuum is the engine. A metal line runs from the manifold to the vac side of the fuel pump. It is connected with about 4" of rubber hose pushed onto the brass tube on the vac pump. There is also a 4" rubber hose on the other brass tube on the top of the pump that goes to a second steel line that runs along the top of the engine towards the fire wall. There is then a piece of rubber tube that goes through the fire wall and comes to a little pot metal Tee. One side of this goes to the Heater temp controller the other side goes to the dash nob. And finally a rubber tube runs from the dash nob to the vacuum motor. The Dash knob can control the wiper speed which was much more difficult with electric in the '50's. Also there is a rubber hose from the control valve to the flying saucer valve that sits on the front of the intake manifold. this is the source for the hot water for the heater. There are no clamps on any of these vacuum lines.

The vacuum motor is actually quite powerful. If yours isn't working well at idle speed and the engine is making good vacuum then it is likely that the grease in it has gotten dried and hard. Try a direct tube from the intake manifold to the vacuum motor to be sure it is working OK. If not try squirting a little ATF into it and working it back and forth by hand until it frees up. Almost needless to say any leaks of air into all these hoses and fittings will make the wipers work badly or not at all.