You do not need to publish this list, because it is already stored in the database, and you even have a repository to retrieve it, right? Therefore, the only thing that needs to be published is the choice of the user, since this is the only thing you do not know. In the POST action, restore the list in your view model using the repository, just as you did in the GET action that displayed the form.
Anyway, is there POST extra data for the controller outside the model property?
Of course, just include them as input fields so that their values are sent via POST and into your controller action:
[HttpPost]
public ActionResult Index(SomeViewModel model, string param1, string, param2)
{
...
}
: .