Is this the actuator behind the radio or the one at the sidewall?
07 Mustang GT - they have 2 actuators, one with the arm and peg (both pictures have the actuator arm). One is behind the radio to the left of the glove box. This actuator has a "gear", no arm while the other on the sidewall side has an arm.
This is the actuator between the radio and glove box that moves the air from floor/dash vents/defrost. The one located at the sidewall is for the blend door function between hot and cold. As for the gear you are referring to, this is a picture of the exact part and identical to the one in my 06 I replaced. Mine did not have a gear. It utilized an arm. This should be the exact replacement for your 07.
I actually had to replace both of these on my 06, and both have an arm and looked almost identical. I went and pulled some from our stock to verify as I did this a few years ago, and they both look almost identical. If yours does indeed have a gear, if you can, shoot me an email at Karson.Swartz@latemodelrestoration.com with a picture and if there are any part numbers on it, list those and I'll do some digging and figure out what it is you have.