The issue I see with replacing a random rubbish model with the spike strip model, is that they would appear randomly throughout the world.
My suggestion is looking in to, or contacting the person responsible for making the "Policing Tools" mod. From what I can tell about it by it's installation, is that nothing from the original game is actually replaced in order for them to add a radar gun model. I would say this would be the best method for adding them providing the information on how to do this is available.