The snap ring I have is angled on the ends, and it fits in the groove without the washer installed. The washer is also .062 of an inch and has two anti rotation tabs. There isn't enough clearance for both of them, and the washer blocks the snap ring entrance, about halfway, when it's installed

I verified that the cam, and the sprag is seated well but I will tap the cam gently tomorrow with a round brass shaft to ensure that it's seated all the way. I don't have any way of fitting it in my little press.

I read that there are different drums that were used in the 727 and A518, and sometimes get mixed up. One used a delrin plastic washer and apparently didn't have as deep of an indent for the washer, from what I understood. When I was tearing down this trans I didn't find any kind of washer in that drum. I kept all the used parts just in case and I didn't see anything like it when I went through them again. I also noticed that my drum doesn't look like any of the A518 drums I'm seeing. It looks like a 46re drum. Does that change anything?

If I sand the non indented side of the washer to make this all fit, am I going to hurt anything?

Thank you for your assessment of the overdrive. I used a homemade tool to press the OD unit, but I used my alignment tool to make sure everything was lined up, and after installing the overdrive housing I found that it had stayed aligned. The third time installing the housing was much easier and it just kind of drew down into place.