I have a newer stainless Marlin SBL in 45/70 and decided to put in a one piece Wild West Ejector. I read the reviews from Brownells and quite a few say they had to be fitted and were a pain and so on. Others say they were a drop in. One gentlemen had the theory that older rifles had to be fitted and new ones not so much. I took a chance. Mine dropped right in and the action is now smoother than with the OEM.
Don't get me wrong. My old JM Marlin rifles are much better crafted but the ones, contrary to popular rumors, actually do work. So why did I put one in? Well, I had a coupon and it was shiny...turns out it ejects better too.