Not necessarily he could've gotten one with multiple forms like Kreshi'sâ¢ Goku. In the case that you did then replace the SS model in your ESF folder with SS3. Just go to My computer>C drive>program files>Valve>Steam>Steam apps> Half life>ESF>Models.
Just go to My computer>C drive>program files>Valve>Steam>Steam apps> Half life>ESF>Models>SSj Goku. Then take the one that you downloaded and put it in the ssj Goku folder instead. And what ever model you put in the SSJ Goku folder he will turn into when he goes ss. Make sure you back up the current model in your Ssj goku folder. then take the ssj goku model thats currently in the folder and delete it or something and put the new one in. Don't put both of them in there make sure there is just one.