Shotgun Boogie Gun Works adjustable trigger kit # 2 for competition rifles, model Uberti ’73

Includes allen wrench, trigger, sear, trigger spring, washer between trigger spring and screw, screws and safety bar spring.

While this kit is easily installed, it is not drop-in, it requires fitting by a competent Gunsmith.
And most important: The position of the trigger IS NOT ADJUSTABLE!

See also the article in Cowboy Chronicle January 2015 from Larsen E. Pettifogger. Pages 36-45:

Because of the variations in manufacturers tolerances, I simply cannot guarantee that my parts will function perfectly without being fitted by a competent gunsmith. I recommend that you employ the services of a gunsmith who is familiar with both these firearms and my kits. Of course, I developed these kits, and am glad to guarantee the work, if I fit them.