I fixed it. If you are having the same problem I will demonstrate how to fix it, download the replace vehicles you want, then go to this link https://www.gta5-mods.com/tools/addon-creator-vehicles-v1-0-7ddf2ca5-ffdf-45e3-93f5-fd8fe36f3de5 , download that, name the addon as police, police2 police3 and so on. Make sure you go to your DLC Packs inorder for the addon to create it. after that put the YFT in x64, levels, gta 5, vehicles, vehicles.rpf , then go to mods, update, update.rpf , common, data, dlclist and import the names you have then click save.
Your welcome and enjoy.