How can I change the columns displayed on a search via lookup?

I am trying to customize the columns that are displayed when a user searches in an Account lookup field.  It looks like the Display Template should be the solution.  However, when I change the Option Source to Model and add the merge fields that I want to display, the lookup search breaks.  

These are the steps to reproduce what I’m experiencing:
In Skuid:
1. Select the lookup field on the edit page
2. Click search tab
3. Change Option Source to Model
4. Add merge fields ( in my case LastName, FirstName, Email, Phone )
5. Save changes

In Service Console:
1. Refresh page
2. Enter Account Name into lookup field
3. At this point the search never finishes

If I use the automatic Option Source I don’t have access to the fields I want to display.  Am I using the Display Template in the correct manner?