OK, I got the sear cage installed successfully. Even with the leg of the sear spring in the notch and out of the way, the slide was stopping just after the ejector went under the slide. I installed a couple of TA90 slides on the frame and they would go all the way forward and back with no problem. After looking at it for a while I figured out that the top of the ejector was making contact with the slide. Interestingly, the two TA90's have an additional cut in the slide just the width of the ejector that's cut just deep enough to allow the ejector to go through without touching the slide. I decided that my best bet would be to file down the top of the ejector as machining the slide would be a costly ordeal. I tried using a hand file, but it was hard as can be and progress was almost not measurable. I took it over to my bench grinder and took the top of the ejector down just a tap at a time. After several taps and fitting trials, I had the ejector going through the slide with no resistance. I then used a hand file to get the top of the ejector perfectly flat. There is of course no way to know for sure, but I'd bet that the original ejector broke due to contact with the underside of the slide.
Unfortunately, there's now a new problem. When the pistol is cocked to single action mode, the hammer falls to half-cock as the trigger is pulled. It wasn't doing this before, but I'm guessing that a slight difference in the dimensions of the sear cage is allowing this to happen. The SA trigger was very light before, so perhaps someone messed with it previously or it was just very light from the factory. Any idea what I should do to fix this problem?