My rx7 is without a mechanism to open the moon roof.
I am not sure what the stock mechanism is? Electric/Manuel, there is a single hole in the headliner about the size of a fifty cent, right under the screw gear.

Is there another car that has the same mechanism that you could swap from or is it better to buy a new unit if, they make something?

 

gotta trade someone for a shell that has a sunroof or you have to remove your windshield and hatch and weld in a new moonroof ready roof section. moonroof and non-moonroof sections of the car are built and reinforced differently. IMO its not safe to add a sunroof to a solid roof car. Along with possibly ruining the chassis you don't have provisions to drain away water that gets past the seals like a factory moonroof equipped car.

 

Maybe I was not clear, My car has a moon roof, it came factory, but the mechanism on the inside of the car to open the moon roof is missing and I dont know if it is a electric motor or a crank, you can see the screw gear under the headliner, hopefully this is a little clearer

 

What year is your car?

 

It is an 1988