this isn't really dealing with power door locks, but more the parts that go into them... I have a 64 ford thunderbird, it has vacuum doorlocks, trunk release, rear vents, ebrake release, and a couple other things... what i'm in the process of doing is getting rid of the vacuum internal pieces, since i can't get new actuators, only used ones, that may or may not be good anymore. so here is the real question :
My rear vents have 2 vacuum actuators one for the left vent and one for the right (they are just fresh air vents for defrosting and clearing smoke out of the car) the vacuum actuators have about 1" worth of travel... when the vent is opened up the vacuum is applied to the actuator and pulls the vent open. there is a little bit of pressure that is needed to get passed the "spring return" that the vents have. (the internal vacuum system draws 18lbs of mercury i believe is what the number is)

Now i'm thinking to do away with the vent actuators i could possibly use power door lock actuators/solenoids (the one that pulls and unlocks/locks the doors)
1. how much of a distance do these actuators pull... 1", 1/2", 2"?
2. Will the actuators remain fully closed, with the pressure of a spring return of about 4-10lbs (i'm not sure about the actual pressure i'm just guessing)?
3. Are these door lock actuators actually really big because i have about 4-5" worth of depth in order to mount them (from the front of the pull to the back of the actuator.

There is a wide variety of actuators and solenoids out there.
Try www.autoloc.com . The Canadian distributor is here in BC, so most everything is available through your local car stereo store or auto parts store.

mmartin - you should stop in at a car audio shop and have a look at an actuator to see how big they are.

1) They stroke about 1.25" or so.
2) Lose the spring.