I have an omega roller sear and trigger kit n 2 of my cockers, and they are smooth and nice.
Been running for 2 years with one, and 1 year with the other, no problems. Makes your pull like butter, especially in a benchmark frame.
For your stock frame.. you may have issues and have to get the sear modded. I cant think of a retro sear kit past something from AKA or shocktech.