Alternative to list item master-detail view

I have a list of items. All having the same default details. User is allowed to... 1. Change defaults for all the items at 1 shot. 2. Filter for some items and change the default value(s). What is the best way to allow the user to do that? The master-detail view will not help as all the list items have the same defaults.

Here is a rough sketch. Defaults for all items are shown in one section. User can filter for different items and change the defaults as well.