create a new folder and name it smv4 place it in your vehicles folder, copy everything in your v4 pack and paste it in the smv4 folder you made, than copy and paste gravediggerflare and put it in your smv4 folder, than go to your separate truck and copy everything from it and paste it in our smv4 folder, than clear and regain the cache, than try, some trucks may be missing some parts but if you download more trucks than they might have the parts the truck needs
when you download a truck don't put it in your packs put it in downloads before you put it in the smv4 folder
erase the old v4 pack