My friend has a sporterized 03-A3 project with a Mashburn trigger. It needs some fitting as the sear is a bit high. How are these as far as quality? Do these hold a premium as far as being a little rarer and also from a big name from the past? What would the trigger be worth?

IMO they're not worth the time to mess with when you can buy a Timney that fits out of the box.

That was always in the back of my mind.