You need to take everything that is not factory off of the frame. When a conversion is done, the way I understand it, they drill another pin hole above the trigger and attach the newer trigger assembly to the frame. This allows the frame to open better and also should make it more compatible with newer barrels. You will still have the old trigger assembly pin hole toward the front of the frame. Sometimes it will work with the old and the new barrels and sometimes you have to have certain barrels matched to the frame. That is why I sent the 30-30 barrel with the frame - to make sure it would work when it came back. If I had a pistol with an aftermarket trigger spring, I would probably take it out before I sent it back.
Also, from what I have heard, the trigger adjustment will be better than the original old style. I don't know that for sure, but that is what I have been hearing.