Help!

I have the the 5124443AB as shown below
Other than internal electronics, will it fit on the car? I really don't want to take the car apart and then find out it won't work.

The photos of both the old siren and the new 512443AA show a threaded hole for a stud. The one I've attached has a stud. And, yes, I've checked under it and it is solid plastic.

Help?