Below is a mount I designed to get back and forth movement from the "deer motor" .....5rpm Synchronous motor.
You can cut the groove for as much movement you want and the screw is a easy way to adjust it. This motor fits in 2 inch PVC and you cutout a spot on both sides for the mount flaps to sit in. I used zip ties to hold it in place.
Back when I was selling the motor someone asked me to figure out a housing and a way to easily mount these to PVC and adjustable back and forth movement. I no longer sell them but it's easy to make. My moto in prop making is ....cheap, easy, simple works best
Here's another way. This is 5rpm Synchronous motor in a case
Here's a actual deer motor using screws to get the back and forth movement