My favorites for building into rifles are the original Remington actions, or Swede and Danish actions. The Swedish Husqvarna are the cleanest looking, as the Danish Carl Gustav often had those set screws retaing pins, and a lot of extra stamps. The Huskys have clean receivers like the Remingtons have.
With the availability of leftover Remington parts from their run in the late 1990's it makes the trigger plates much less work. Fitting one of the late Rem. plates takes way less time than reshaping a military plate.