I'll add that it seems a lot easier to find early than late-model parts, and I wonder if a late action and early action are the same aside from the various drilled and tapped holes for sights and scopes. In other words, if the pin holes and machining are the same and would allow a complete early model trigger / bolt setup to be used in a late action. You obviously couldn't swap just the bolts because they wouldn't work with the opposite generation's trigger.
