I'm in the process of getting my PW's working in my 69. Actually it's been in process for ~1yr. I also had none of the motors operating. The likelyhood that all 4 motors are bad is very slim.
Just as CR stated, you can make a jumper wire to determine which windows work. Each motor has a yellow & red two prong connector. If you put 12v to one wire and ground the other (I had to run it all the way back to the battery's negative), the window motor should operate (or try to operate) in one direction. If you reverse the connection the motor will operate (or attempt to operate) in the opposite direction.
Before you do that, if the panels aren't removed yet, I'd check the main power into the circuit which James C referenced. There's a circuit breaker leading to a relay attached to one side of the solenoid. The relay has black, red, and blue wire wires running to it. If I recall correctly, the red wire operates the relay coil when the ignition switch is on. The black and blue wires provide power to the window motors themselves when the relay is engaged. You can easily test the circuit breaker & relay by removing the blue wire from the relay and connecting it directly to the positive side of the battery. If you now have power to the windows, then the problem is the circuit breaker or relay and you don't have to go messing w/switches & internal wiring.
Even after you get things settled there's more to this system. It turns out that if you've never cleaned out the tracks they're probably gunked up w/petrified grease. I had to use brake cleaner on them, but if you're not going to remove them from the car, you'll want to use a less harsh degreaser and then regrease.
Finally, the rear motors are special units called "pancake" motors since they're big, flat, and shaped like an 8 (you thought I'd say pancake :-D). They are also flat like a pancake. These units probably need to be reconditioned if they work at all. Check w/Don Rush.
BTW, there are TONS of threads on power windows in this bulletin board. YHou might want to do a search and check them out.