I was wondering about the condition of the attached picture of my reverse drum. I don’t feel any ridges and everything feels smooth.

Clean the surface where the band rides and check it with a straight edge. If it dishes in the middle of where the band rides, then you need a new oem drum or a good used one that is "flat".

I had to replace it during the rebuild on my Tahoe’s 60e a few months back. If you see a gap of light under the straight edge like this replace it.