I installed the ejector assembly from the Uberti 72 Opentop, purchased from VTIgunparts. The assembly uses the former loading lever pivot hole but uses the Opentop retaining screw, so purchase that as well. The thread pitch is different on the Opentop ejector housing, for some reason, so the lever pivot screw cannot be used. You have to counterbore the right side of the formerly threaded pivot hole to fit the stud on the ejector housing.
You have to mill a groove in the barrel to seat the ejector assembly in the correct place to align with the chambers for ejection, and that is the trickiest part of the installation, getting the groove cut (7/16 ball end mill) to the proper depth and the centerline located properly above the screw and parrallel to the bore.